diff --git a/examples/virtual_methods/base_button/mod.rs b/examples/virtual_methods/base_button/mod.rs
index 75cbf279260b..afb76398665a 100644
--- a/examples/virtual_methods/base_button/mod.rs
+++ b/examples/virtual_methods/base_button/mod.rs
@@ -63,6 +63,8 @@ impl<O: IsA<BaseButton>> BaseButtonExt for O {}
 pub trait BaseButtonImpl: ButtonImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<gtk::Widget>,
+    <Self as ObjectSubclass>::Type: IsA<gtk::Button>,
 {
     /// Default implementation of a virtual method.
     ///
@@ -91,6 +93,8 @@ where
 pub trait BaseButtonImplExt: BaseButtonImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<gtk::Widget>,
+    <Self as ObjectSubclass>::Type: IsA<gtk::Button>,
 {
     /// Retrieves the parent class' implementation of the virtual method and
     /// calls it.
@@ -113,12 +117,20 @@ where
     }
 }
 
-impl<T: BaseButtonImpl> BaseButtonImplExt for T where <T as ObjectSubclass>::Type: IsA<glib::Object> {}
+impl<T: BaseButtonImpl> BaseButtonImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<gtk::Widget>,
+    <T as ObjectSubclass>::Type: IsA<gtk::Button>,
+{
+}
 
 /// This allows to implement subclasses of `BaseButton`.
 unsafe impl<T: BaseButtonImpl> IsSubclassable<T> for BaseButton
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<gtk::Widget>,
+    <T as ObjectSubclass>::Type: IsA<gtk::Button>,
 {
     /// Called whenever the class of a `BaseButton` subclass is initialized,
     /// i.e. usually right before the first instance of it is created.
diff --git a/gdk4/src/subclass/content_provider.rs b/gdk4/src/subclass/content_provider.rs
index 114ecad20e59..1886d1e85e30 100644
--- a/gdk4/src/subclass/content_provider.rs
+++ b/gdk4/src/subclass/content_provider.rs
@@ -12,6 +12,7 @@ use crate::{ffi, prelude::*, subclass::prelude::*, Clipboard, ContentFormats, Co
 pub trait ContentProviderImpl: ObjectImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<ContentProvider>,
 {
     fn content_changed(&self) {
         self.parent_content_changed()
@@ -50,6 +51,7 @@ where
 pub trait ContentProviderImplExt: ContentProviderImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<ContentProvider>,
 {
     fn parent_content_changed(&self) {
         unsafe {
@@ -261,14 +263,17 @@ where
     }
 }
 
-impl<T: ContentProviderImpl> ContentProviderImplExt for T where
-    <T as ObjectSubclass>::Type: IsA<glib::Object>
+impl<T: ContentProviderImpl> ContentProviderImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<ContentProvider>,
 {
 }
 
 unsafe impl<T: ContentProviderImpl> IsSubclassable<T> for ContentProvider
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<ContentProvider>,
 {
     fn class_init(class: &mut glib::Class<Self>) {
         Self::parent_class_init::<T>(class);
@@ -289,6 +294,7 @@ unsafe extern "C" fn content_provider_content_changed<T: ContentProviderImpl>(
     ptr: *mut ffi::GdkContentProvider,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<ContentProvider>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -301,6 +307,7 @@ unsafe extern "C" fn content_provider_attach_clipboard<T: ContentProviderImpl>(
     clipboard_ptr: *mut ffi::GdkClipboard,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<ContentProvider>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -314,6 +321,7 @@ unsafe extern "C" fn content_provider_detach_clipboard<T: ContentProviderImpl>(
     clipboard_ptr: *mut ffi::GdkClipboard,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<ContentProvider>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -327,6 +335,7 @@ unsafe extern "C" fn content_provider_formats<T: ContentProviderImpl>(
 ) -> *mut ffi::GdkContentFormats
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<ContentProvider>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -339,6 +348,7 @@ unsafe extern "C" fn content_provider_storable_formats<T: ContentProviderImpl>(
 ) -> *mut ffi::GdkContentFormats
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<ContentProvider>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -356,6 +366,7 @@ unsafe extern "C" fn content_provider_write_mime_type_async<T: ContentProviderIm
     user_data: glib::ffi::gpointer,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<ContentProvider>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -418,6 +429,7 @@ unsafe extern "C" fn content_provider_get_value<T: ContentProviderImpl>(
 ) -> glib::ffi::gboolean
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<ContentProvider>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gdk4/src/subclass/paintable.rs b/gdk4/src/subclass/paintable.rs
index 7a447cbb9391..98d2aeb896d3 100644
--- a/gdk4/src/subclass/paintable.rs
+++ b/gdk4/src/subclass/paintable.rs
@@ -11,6 +11,7 @@ use crate::{ffi, prelude::*, subclass::prelude::*, Paintable, PaintableFlags, Sn
 pub trait PaintableImpl: ObjectImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Paintable>,
 {
     #[doc(alias = "get_current_image")]
     fn current_image(&self) -> Paintable {
@@ -43,6 +44,7 @@ where
 pub trait PaintableImplExt: PaintableImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Paintable>,
 {
     fn parent_current_image(&self) -> Paintable {
         unsafe {
@@ -132,11 +134,17 @@ where
     }
 }
 
-impl<T: PaintableImpl> PaintableImplExt for T where <T as ObjectSubclass>::Type: IsA<glib::Object> {}
+impl<T: PaintableImpl> PaintableImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Paintable>,
+{
+}
 
 unsafe impl<T: PaintableImpl> IsImplementable<T> for Paintable
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Paintable>,
 {
     fn interface_init(iface: &mut glib::Interface<Self>) {
         let iface = iface.as_mut();
@@ -155,6 +163,7 @@ unsafe extern "C" fn paintable_get_current_image<T: PaintableImpl>(
 ) -> *mut ffi::GdkPaintable
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Paintable>,
 {
     let instance = &*(paintable as *mut T::Instance);
     let imp = instance.imp();
@@ -167,6 +176,7 @@ unsafe extern "C" fn paintable_get_flags<T: PaintableImpl>(
 ) -> ffi::GdkPaintableFlags
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Paintable>,
 {
     let instance = &*(paintable as *mut T::Instance);
     let imp = instance.imp();
@@ -179,6 +189,7 @@ unsafe extern "C" fn paintable_get_intrinsic_width<T: PaintableImpl>(
 ) -> i32
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Paintable>,
 {
     let instance = &*(paintable as *mut T::Instance);
     let imp = instance.imp();
@@ -191,6 +202,7 @@ unsafe extern "C" fn paintable_get_intrinsic_height<T: PaintableImpl>(
 ) -> i32
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Paintable>,
 {
     let instance = &*(paintable as *mut T::Instance);
     let imp = instance.imp();
@@ -203,6 +215,7 @@ unsafe extern "C" fn paintable_get_intrinsic_aspect_ratio<T: PaintableImpl>(
 ) -> f64
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Paintable>,
 {
     let instance = &*(paintable as *mut T::Instance);
     let imp = instance.imp();
@@ -217,6 +230,7 @@ unsafe extern "C" fn paintable_snapshot<T: PaintableImpl>(
     height: f64,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Paintable>,
 {
     let instance = &*(paintable as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/accessible.rs b/gtk4/src/subclass/accessible.rs
index 80c3eb920a2c..cd8e98e7ac0b 100644
--- a/gtk4/src/subclass/accessible.rs
+++ b/gtk4/src/subclass/accessible.rs
@@ -15,6 +15,7 @@ use crate::{
 pub trait AccessibleImpl: ObjectImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Accessible>,
 {
     #[doc(alias = "get_platform_state")]
     fn platform_state(&self, state: AccessiblePlatformState) -> bool {
@@ -50,6 +51,7 @@ where
 pub trait AccessibleImplExt: AccessibleImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Accessible>,
 {
     fn parent_platform_state(&self, state: AccessiblePlatformState) -> bool {
         unsafe {
@@ -167,11 +169,17 @@ where
     }
 }
 
-impl<T: AccessibleImpl> AccessibleImplExt for T where <T as ObjectSubclass>::Type: IsA<glib::Object> {}
+impl<T: AccessibleImpl> AccessibleImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Accessible>,
+{
+}
 
 unsafe impl<T: AccessibleImpl> IsImplementable<T> for Accessible
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Accessible>,
 {
     fn interface_init(iface: &mut glib::Interface<Self>) {
         let iface = iface.as_mut();
@@ -191,6 +199,7 @@ unsafe extern "C" fn accessible_get_platform_state<T: AccessibleImpl>(
 ) -> glib::ffi::gboolean
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Accessible>,
 {
     let instance = &*(accessible as *mut T::Instance);
     let imp = instance.imp();
@@ -207,6 +216,7 @@ unsafe extern "C" fn accessible_get_bounds<T: AccessibleImpl>(
 ) -> glib::ffi::gboolean
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Accessible>,
 {
     let instance = &*(accessible as *mut T::Instance);
     let imp = instance.imp();
@@ -228,6 +238,7 @@ unsafe extern "C" fn accessible_get_at_context<T: AccessibleImpl>(
 ) -> *mut ffi::GtkATContext
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Accessible>,
 {
     let instance = &*(accessible as *mut T::Instance);
     let imp = instance.imp();
@@ -240,6 +251,7 @@ unsafe extern "C" fn accessible_get_accessible_parent<T: AccessibleImpl>(
 ) -> *mut ffi::GtkAccessible
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Accessible>,
 {
     let instance = &*(accessible as *mut T::Instance);
     let imp = instance.imp();
@@ -252,6 +264,7 @@ unsafe extern "C" fn accessible_get_first_accessible_child<T: AccessibleImpl>(
 ) -> *mut ffi::GtkAccessible
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Accessible>,
 {
     let instance = &*(accessible as *mut T::Instance);
     let imp = instance.imp();
@@ -264,6 +277,7 @@ unsafe extern "C" fn accessible_get_next_accessible_sibling<T: AccessibleImpl>(
 ) -> *mut ffi::GtkAccessible
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Accessible>,
 {
     let instance = &*(accessible as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/accessible_range.rs b/gtk4/src/subclass/accessible_range.rs
index cdf190cf4bf9..59d52b5e7097 100644
--- a/gtk4/src/subclass/accessible_range.rs
+++ b/gtk4/src/subclass/accessible_range.rs
@@ -6,11 +6,13 @@
 
 use glib::translate::*;
 
-use crate::{ffi, prelude::*, subclass::prelude::*, AccessibleRange};
+use crate::{ffi, prelude::*, subclass::prelude::*, AccessibleRange, Widget};
 
 pub trait AccessibleRangeImpl: WidgetImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Widget>,
+    <Self as ObjectSubclass>::Type: IsA<AccessibleRange>,
 {
     fn set_current_value(&self, value: f64) -> bool {
         self.parent_set_current_value(value)
@@ -20,6 +22,8 @@ where
 pub trait AccessibleRangeImplExt: AccessibleRangeImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Widget>,
+    <Self as ObjectSubclass>::Type: IsA<AccessibleRange>,
 {
     // Returns true if the operation was performed, false otherwise
     fn parent_set_current_value(&self, value: f64) -> bool {
@@ -43,14 +47,19 @@ where
     }
 }
 
-impl<T: AccessibleRangeImpl> AccessibleRangeImplExt for T where
-    <T as ObjectSubclass>::Type: IsA<glib::Object>
+impl<T: AccessibleRangeImpl> AccessibleRangeImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<AccessibleRange>,
 {
 }
 
 unsafe impl<T: AccessibleRangeImpl> IsImplementable<T> for AccessibleRange
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<AccessibleRange>,
 {
     fn interface_init(iface: &mut glib::Interface<Self>) {
         let iface = iface.as_mut();
@@ -65,6 +74,8 @@ unsafe extern "C" fn accessible_range_set_current_value<T: AccessibleRangeImpl>(
 ) -> glib::ffi::gboolean
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<AccessibleRange>,
 {
     let instance = &*(accessible_range as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/actionable.rs b/gtk4/src/subclass/actionable.rs
index 448936960b14..213e791f252c 100644
--- a/gtk4/src/subclass/actionable.rs
+++ b/gtk4/src/subclass/actionable.rs
@@ -6,11 +6,13 @@
 
 use glib::{translate::*, GString, Variant};
 
-use crate::{ffi, prelude::*, subclass::prelude::*, Actionable};
+use crate::{ffi, prelude::*, subclass::prelude::*, Actionable, Widget};
 
 pub trait ActionableImpl: WidgetImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Widget>,
+    <Self as ObjectSubclass>::Type: IsA<Actionable>,
 {
     #[doc(alias = "get_action_name")]
     fn action_name(&self) -> Option<GString>;
@@ -23,6 +25,8 @@ where
 pub trait ActionableImplExt: ActionableImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Widget>,
+    <Self as ObjectSubclass>::Type: IsA<Actionable>,
 {
     fn parent_action_name(&self) -> Option<GString> {
         unsafe {
@@ -91,11 +95,19 @@ where
     }
 }
 
-impl<T: ActionableImpl> ActionableImplExt for T where <T as ObjectSubclass>::Type: IsA<glib::Object> {}
+impl<T: ActionableImpl> ActionableImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Actionable>,
+{
+}
 
 unsafe impl<T: ActionableImpl> IsImplementable<T> for Actionable
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Actionable>,
 {
     fn interface_init(iface: &mut glib::Interface<Self>) {
         let iface = iface.as_mut();
@@ -112,6 +124,8 @@ unsafe extern "C" fn actionable_get_action_name<T: ActionableImpl>(
 ) -> *const libc::c_char
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Actionable>,
 {
     let instance = &*(actionable as *mut T::Instance);
     let imp = instance.imp();
@@ -124,6 +138,8 @@ unsafe extern "C" fn actionable_get_action_target_value<T: ActionableImpl>(
 ) -> *mut glib::ffi::GVariant
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Actionable>,
 {
     let instance = &*(actionable as *mut T::Instance);
     let imp = instance.imp();
@@ -136,6 +152,8 @@ unsafe extern "C" fn actionable_set_action_name<T: ActionableImpl>(
     name: *const libc::c_char,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Actionable>,
 {
     let instance = &*(actionable as *mut T::Instance);
     let imp = instance.imp();
@@ -148,6 +166,8 @@ unsafe extern "C" fn actionable_set_action_target_value<T: ActionableImpl>(
     value: *mut glib::ffi::GVariant,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Actionable>,
 {
     let instance = &*(actionable as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/adjustment.rs b/gtk4/src/subclass/adjustment.rs
index a7f218969371..48ba7d7c83aa 100644
--- a/gtk4/src/subclass/adjustment.rs
+++ b/gtk4/src/subclass/adjustment.rs
@@ -10,6 +10,7 @@ use crate::{ffi, prelude::*, subclass::prelude::*, Adjustment};
 pub trait AdjustmentImpl: ObjectImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Adjustment>,
 {
     fn changed(&self) {
         self.parent_changed()
@@ -23,6 +24,7 @@ where
 pub trait AdjustmentImplExt: AdjustmentImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Adjustment>,
 {
     fn parent_changed(&self) {
         unsafe {
@@ -45,11 +47,17 @@ where
     }
 }
 
-impl<T: AdjustmentImpl> AdjustmentImplExt for T where <T as ObjectSubclass>::Type: IsA<glib::Object> {}
+impl<T: AdjustmentImpl> AdjustmentImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Adjustment>,
+{
+}
 
 unsafe impl<T: AdjustmentImpl> IsSubclassable<T> for Adjustment
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Adjustment>,
 {
     fn class_init(class: &mut glib::Class<Self>) {
         Self::parent_class_init::<T>(class);
@@ -65,6 +73,7 @@ where
 unsafe extern "C" fn adjustment_changed<T: AdjustmentImpl>(ptr: *mut ffi::GtkAdjustment)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Adjustment>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -75,6 +84,7 @@ where
 unsafe extern "C" fn adjustment_value_changed<T: AdjustmentImpl>(ptr: *mut ffi::GtkAdjustment)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Adjustment>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/application.rs b/gtk4/src/subclass/application.rs
index 841b2745195d..0c9e0b7d75c6 100644
--- a/gtk4/src/subclass/application.rs
+++ b/gtk4/src/subclass/application.rs
@@ -11,6 +11,7 @@ pub trait GtkApplicationImpl: ApplicationImpl + ObjectImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
     <Self as ObjectSubclass>::Type: IsA<gio::Application>,
+    <Self as ObjectSubclass>::Type: IsA<Application>,
 {
     fn window_added(&self, window: &Window) {
         self.parent_window_added(window)
@@ -25,6 +26,7 @@ pub trait GtkApplicationImplExt: GtkApplicationImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
     <Self as ObjectSubclass>::Type: IsA<gio::Application>,
+    <Self as ObjectSubclass>::Type: IsA<Application>,
 {
     fn parent_window_added(&self, window: &Window) {
         unsafe {
@@ -57,6 +59,7 @@ impl<T: GtkApplicationImpl> GtkApplicationImplExt for T
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
     <T as ObjectSubclass>::Type: IsA<gio::Application>,
+    <T as ObjectSubclass>::Type: IsA<Application>,
 {
 }
 
@@ -64,6 +67,7 @@ unsafe impl<T: GtkApplicationImpl> IsSubclassable<T> for Application
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
     <T as ObjectSubclass>::Type: IsA<gio::Application>,
+    <T as ObjectSubclass>::Type: IsA<Application>,
 {
     fn class_init(class: &mut ::glib::Class<Self>) {
         // Override the original `GtkApplication` startup implementation so that
@@ -118,6 +122,7 @@ unsafe extern "C" fn application_window_added<T: GtkApplicationImpl>(
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
     <T as ObjectSubclass>::Type: IsA<gio::Application>,
+    <T as ObjectSubclass>::Type: IsA<Application>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -131,6 +136,7 @@ unsafe extern "C" fn application_window_removed<T: GtkApplicationImpl>(
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
     <T as ObjectSubclass>::Type: IsA<gio::Application>,
+    <T as ObjectSubclass>::Type: IsA<Application>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/application_window.rs b/gtk4/src/subclass/application_window.rs
index ba58c37261f7..ba880b7edfae 100644
--- a/gtk4/src/subclass/application_window.rs
+++ b/gtk4/src/subclass/application_window.rs
@@ -4,15 +4,22 @@
 //! Traits intended for subclassing
 //! [`ApplicationWindow`](crate::ApplicationWindow).
 
-use crate::{prelude::*, subclass::prelude::*, ApplicationWindow};
+use crate::{prelude::*, subclass::prelude::*, ApplicationWindow, Widget, Window};
 
 pub trait ApplicationWindowImpl: WindowImpl + 'static
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Widget>,
+    <Self as ObjectSubclass>::Type: IsA<Window>,
+    <Self as ObjectSubclass>::Type: IsA<ApplicationWindow>,
 {
 }
 
-unsafe impl<T: ApplicationWindowImpl> IsSubclassable<T> for ApplicationWindow where
-    <T as ObjectSubclass>::Type: IsA<glib::Object>
+unsafe impl<T: ApplicationWindowImpl> IsSubclassable<T> for ApplicationWindow
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Window>,
+    <T as ObjectSubclass>::Type: IsA<ApplicationWindow>,
 {
 }
diff --git a/gtk4/src/subclass/box_.rs b/gtk4/src/subclass/box_.rs
index 9d23a22ee9fe..6b9bdf44f837 100644
--- a/gtk4/src/subclass/box_.rs
+++ b/gtk4/src/subclass/box_.rs
@@ -3,15 +3,20 @@
 // rustdoc-stripper-ignore-next
 //! Traits intended for subclassing [`Box`](crate::Box).
 
-use crate::{prelude::*, subclass::prelude::*, Box};
+use crate::{prelude::*, subclass::prelude::*, Box, Widget};
 
 pub trait BoxImpl: WidgetImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Widget>,
+    <Self as ObjectSubclass>::Type: IsA<Box>,
 {
 }
 
-unsafe impl<T: BoxImpl> IsSubclassable<T> for Box where
-    <T as ObjectSubclass>::Type: IsA<glib::Object>
+unsafe impl<T: BoxImpl> IsSubclassable<T> for Box
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Box>,
 {
 }
diff --git a/gtk4/src/subclass/buildable.rs b/gtk4/src/subclass/buildable.rs
index 86a4ee419ccc..01918dc97a44 100644
--- a/gtk4/src/subclass/buildable.rs
+++ b/gtk4/src/subclass/buildable.rs
@@ -13,6 +13,7 @@ use crate::{ffi, prelude::*, subclass::prelude::*, Buildable, Builder};
 pub trait BuildableImpl: ObjectImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Buildable>,
 {
     fn set_id(&self, id: &str) {
         self.parent_set_id(id)
@@ -65,6 +66,7 @@ where
 pub trait BuildableImplExt: BuildableImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Buildable>,
 {
     fn parent_set_id(&self, id: &str) {
         unsafe {
@@ -191,11 +193,17 @@ where
     }
 }
 
-impl<T: BuildableImpl> BuildableImplExt for T where <T as ObjectSubclass>::Type: IsA<glib::Object> {}
+impl<T: BuildableImpl> BuildableImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Buildable>,
+{
+}
 
 unsafe impl<T: BuildableImpl> IsImplementable<T> for Buildable
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Buildable>,
 {
     fn interface_init(iface: &mut glib::Interface<Self>) {
         let iface = iface.as_mut();
@@ -219,6 +227,7 @@ unsafe extern "C" fn buildable_set_id<T: BuildableImpl>(
     id: *const libc::c_char,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Buildable>,
 {
     let instance = &*(buildable as *mut T::Instance);
     let imp = instance.imp();
@@ -232,6 +241,7 @@ unsafe extern "C" fn buildable_get_id<T: BuildableImpl>(
 ) -> *const libc::c_char
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Buildable>,
 {
     let instance = &*(buildable as *mut T::Instance);
     let imp = instance.imp();
@@ -246,6 +256,7 @@ unsafe extern "C" fn buildable_add_child<T: BuildableImpl>(
     typeptr: *const libc::c_char,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Buildable>,
 {
     let instance = &*(buildable as *mut T::Instance);
     let imp = instance.imp();
@@ -265,6 +276,7 @@ unsafe extern "C" fn buildable_set_buildable_property<T: BuildableImpl>(
     valueptr: *const glib::gobject_ffi::GValue,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Buildable>,
 {
     let instance = &*(buildable as *mut T::Instance);
     let imp = instance.imp();
@@ -284,6 +296,7 @@ unsafe extern "C" fn buildable_construct_child<T: BuildableImpl>(
 ) -> *mut glib::gobject_ffi::GObject
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Buildable>,
 {
     let instance = &*(buildable as *mut T::Instance);
     let imp = instance.imp();
@@ -298,6 +311,7 @@ unsafe extern "C" fn buildable_parser_finished<T: BuildableImpl>(
     builderptr: *mut ffi::GtkBuilder,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Buildable>,
 {
     let instance = &*(buildable as *mut T::Instance);
     let imp = instance.imp();
@@ -312,6 +326,7 @@ unsafe extern "C" fn buildable_get_internal_child<T: BuildableImpl>(
 ) -> *mut glib::gobject_ffi::GObject
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Buildable>,
 {
     let instance = &*(buildable as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/builder_scope.rs b/gtk4/src/subclass/builder_scope.rs
index 85ab235f40bc..09dfb7bfff52 100644
--- a/gtk4/src/subclass/builder_scope.rs
+++ b/gtk4/src/subclass/builder_scope.rs
@@ -14,17 +14,23 @@ use crate::{
 pub trait BuilderCScopeImpl: BuilderScopeImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<BuilderScope>,
+    <Self as ObjectSubclass>::Type: IsA<BuilderCScope>,
 {
 }
 
-unsafe impl<T: BuilderCScopeImpl> IsSubclassable<T> for BuilderCScope where
-    <T as ObjectSubclass>::Type: IsA<glib::Object>
+unsafe impl<T: BuilderCScopeImpl> IsSubclassable<T> for BuilderCScope
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<BuilderScope>,
+    <T as ObjectSubclass>::Type: IsA<BuilderCScope>,
 {
 }
 
 pub trait BuilderScopeImpl: ObjectImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<BuilderScope>,
 {
     #[doc(alias = "get_type_from_name")]
     fn type_from_name(&self, builder: &Builder, type_name: &str) -> glib::Type {
@@ -48,6 +54,7 @@ where
 pub trait BuilderScopeImplExt: BuilderScopeImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<BuilderScope>,
 {
     fn parent_type_from_name(&self, builder: &Builder, type_name: &str) -> glib::Type {
         unsafe {
@@ -128,14 +135,17 @@ where
     }
 }
 
-impl<T: BuilderScopeImpl> BuilderScopeImplExt for T where
-    <T as ObjectSubclass>::Type: IsA<glib::Object>
+impl<T: BuilderScopeImpl> BuilderScopeImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<BuilderScope>,
 {
 }
 
 unsafe impl<T: BuilderScopeImpl> IsImplementable<T> for BuilderScope
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<BuilderScope>,
 {
     fn interface_init(iface: &mut glib::Interface<Self>) {
         let iface = iface.as_mut();
@@ -155,6 +165,7 @@ unsafe extern "C" fn builder_scope_get_type_from_name<T: BuilderScopeImpl>(
 ) -> glib::ffi::GType
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<BuilderScope>,
 {
     let instance = &*(builder_scope as *mut T::Instance);
     let imp = instance.imp();
@@ -171,6 +182,7 @@ unsafe extern "C" fn builder_scope_get_type_from_function<T: BuilderScopeImpl>(
 ) -> glib::ffi::GType
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<BuilderScope>,
 {
     let instance = &*(builder_scope as *mut T::Instance);
     let imp = instance.imp();
@@ -190,6 +202,7 @@ unsafe extern "C" fn builder_scope_create_closure<T: BuilderScopeImpl>(
 ) -> *mut glib::gobject_ffi::GClosure
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<BuilderScope>,
 {
     let instance = &*(builder_scope as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/button.rs b/gtk4/src/subclass/button.rs
index 53f0a082eda1..4f2b9e8fd4c5 100644
--- a/gtk4/src/subclass/button.rs
+++ b/gtk4/src/subclass/button.rs
@@ -5,11 +5,13 @@
 
 use glib::translate::*;
 
-use crate::{ffi, prelude::*, subclass::prelude::*, Button};
+use crate::{ffi, prelude::*, subclass::prelude::*, Button, Widget};
 
 pub trait ButtonImpl: WidgetImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Widget>,
+    <Self as ObjectSubclass>::Type: IsA<Button>,
 {
     fn activate(&self) {
         self.parent_activate()
@@ -23,6 +25,8 @@ where
 pub trait ButtonImplExt: ButtonImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Widget>,
+    <Self as ObjectSubclass>::Type: IsA<Button>,
 {
     fn parent_activate(&self) {
         unsafe {
@@ -44,11 +48,19 @@ where
         }
     }
 }
-impl<T: ButtonImpl> ButtonImplExt for T where <T as ObjectSubclass>::Type: IsA<glib::Object> {}
+impl<T: ButtonImpl> ButtonImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Button>,
+{
+}
 
 unsafe impl<T: ButtonImpl> IsSubclassable<T> for Button
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Button>,
 {
     fn class_init(class: &mut glib::Class<Self>) {
         Self::parent_class_init::<T>(class);
@@ -62,6 +74,8 @@ where
 unsafe extern "C" fn button_activate<T: ButtonImpl>(ptr: *mut ffi::GtkButton)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Button>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -72,6 +86,8 @@ where
 unsafe extern "C" fn button_clicked<T: ButtonImpl>(ptr: *mut ffi::GtkButton)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Button>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/cell_area.rs b/gtk4/src/subclass/cell_area.rs
index b28345363f4a..176cc523bee8 100644
--- a/gtk4/src/subclass/cell_area.rs
+++ b/gtk4/src/subclass/cell_area.rs
@@ -66,6 +66,7 @@ impl CellCallbackAllocate {
 pub trait CellAreaImpl: ObjectImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<CellArea>,
 {
     fn cell_properties() -> &'static [ParamSpec] {
         &[]
@@ -227,6 +228,7 @@ where
 pub trait CellAreaImplExt: CellAreaImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<CellArea>,
 {
     // Returns true if the area was successfully activated
     fn parent_activate<P: IsA<CellAreaContext>, W: IsA<Widget>>(
@@ -563,11 +565,17 @@ where
     }
 }
 
-impl<T: CellAreaImpl> CellAreaImplExt for T where <T as ObjectSubclass>::Type: IsA<glib::Object> {}
+impl<T: CellAreaImpl> CellAreaImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellArea>,
+{
+}
 
 unsafe impl<T: CellAreaImpl> IsSubclassable<T> for CellArea
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellArea>,
 {
     fn class_init(class: &mut glib::Class<Self>) {
         Self::parent_class_init::<T>(class);
@@ -617,6 +625,7 @@ unsafe extern "C" fn cell_area_set_cell_property<T: CellAreaImpl>(
     pspecptr: *mut glib::gobject_ffi::GParamSpec,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellArea>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -636,6 +645,7 @@ unsafe extern "C" fn cell_area_get_cell_property<T: CellAreaImpl>(
     pspecptr: *mut glib::gobject_ffi::GParamSpec,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellArea>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -657,6 +667,7 @@ unsafe extern "C" fn cell_area_add<T: CellAreaImpl>(
     rendererptr: *mut ffi::GtkCellRenderer,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellArea>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -673,6 +684,7 @@ unsafe extern "C" fn cell_area_apply_attributes<T: CellAreaImpl>(
     is_expanded: glib::ffi::gboolean,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellArea>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -692,6 +704,7 @@ unsafe extern "C" fn cell_area_remove<T: CellAreaImpl>(
     rendererptr: *mut ffi::GtkCellRenderer,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellArea>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -705,6 +718,7 @@ unsafe extern "C" fn cell_area_is_activatable<T: CellAreaImpl>(
 ) -> glib::ffi::gboolean
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellArea>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -718,6 +732,7 @@ unsafe extern "C" fn cell_area_focus<T: CellAreaImpl>(
 ) -> glib::ffi::gboolean
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellArea>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -730,6 +745,7 @@ unsafe extern "C" fn cell_area_get_request_mode<T: CellAreaImpl>(
 ) -> ffi::GtkSizeRequestMode
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellArea>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -745,6 +761,7 @@ unsafe extern "C" fn cell_area_get_preferred_height<T: CellAreaImpl>(
     natptr: *mut libc::c_int,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellArea>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -768,6 +785,7 @@ unsafe extern "C" fn cell_area_get_preferred_width<T: CellAreaImpl>(
     natptr: *mut libc::c_int,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellArea>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -792,6 +810,7 @@ unsafe extern "C" fn cell_area_get_preferred_width_for_height<T: CellAreaImpl>(
     nat_width_ptr: *mut libc::c_int,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellArea>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -816,6 +835,7 @@ unsafe extern "C" fn cell_area_get_preferred_height_for_width<T: CellAreaImpl>(
     nat_height_ptr: *mut libc::c_int,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellArea>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -841,6 +861,7 @@ unsafe extern "C" fn cell_area_activate<T: CellAreaImpl>(
 ) -> glib::ffi::gboolean
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellArea>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -868,6 +889,7 @@ unsafe extern "C" fn cell_area_snapshot<T: CellAreaImpl>(
     paint_focus: glib::ffi::gboolean,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellArea>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -891,6 +913,7 @@ unsafe extern "C" fn cell_area_create_context<T: CellAreaImpl>(
 ) -> *mut ffi::GtkCellAreaContext
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellArea>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -904,6 +927,7 @@ unsafe extern "C" fn cell_area_copy_context<T: CellAreaImpl>(
 ) -> *mut ffi::GtkCellAreaContext
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellArea>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -922,6 +946,7 @@ unsafe extern "C" fn cell_area_event<T: CellAreaImpl>(
 ) -> glib::ffi::gboolean
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellArea>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -940,6 +965,7 @@ unsafe extern "C" fn cell_area_foreach<T: CellAreaImpl>(
     user_data: glib::ffi::gpointer,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellArea>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -962,6 +988,7 @@ unsafe extern "C" fn cell_area_foreach_alloc<T: CellAreaImpl>(
     user_data: glib::ffi::gpointer,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellArea>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -1009,5 +1036,6 @@ unsafe impl<T: ClassStruct> CellAreaClassExt for T
 where
     T::Type: CellAreaImpl,
     <T::Type as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T::Type as ObjectSubclass>::Type: IsA<CellArea>,
 {
 }
diff --git a/gtk4/src/subclass/cell_area_context.rs b/gtk4/src/subclass/cell_area_context.rs
index 604639bc2519..1ca26f516dab 100644
--- a/gtk4/src/subclass/cell_area_context.rs
+++ b/gtk4/src/subclass/cell_area_context.rs
@@ -14,6 +14,7 @@ use crate::{ffi, prelude::*, subclass::prelude::*, CellAreaContext};
 pub trait CellAreaContextImpl: ObjectImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<CellAreaContext>,
 {
     fn reset(&self) {
         self.parent_reset()
@@ -37,6 +38,7 @@ where
 pub trait CellAreaContextImplExt: CellAreaContextImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<CellAreaContext>,
 {
     fn parent_reset(&self) {
         unsafe {
@@ -116,14 +118,17 @@ where
     }
 }
 
-impl<T: CellAreaContextImpl> CellAreaContextImplExt for T where
-    <T as ObjectSubclass>::Type: IsA<glib::Object>
+impl<T: CellAreaContextImpl> CellAreaContextImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellAreaContext>,
 {
 }
 
 unsafe impl<T: CellAreaContextImpl> IsSubclassable<T> for CellAreaContext
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellAreaContext>,
 {
     fn class_init(class: &mut glib::Class<Self>) {
         Self::parent_class_init::<T>(class);
@@ -144,6 +149,7 @@ unsafe extern "C" fn cell_area_context_reset<T: CellAreaContextImpl>(
     ptr: *mut ffi::GtkCellAreaContext,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellAreaContext>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -158,6 +164,7 @@ unsafe extern "C" fn cell_area_context_get_preferred_height_for_width<T: CellAre
     natural_height: *mut libc::c_int,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellAreaContext>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -174,6 +181,7 @@ unsafe extern "C" fn cell_area_context_get_preferred_width_for_height<T: CellAre
     natural_width: *mut libc::c_int,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellAreaContext>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -189,6 +197,7 @@ unsafe extern "C" fn cell_area_context_allocate<T: CellAreaContextImpl>(
     height: i32,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellAreaContext>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/cell_editable.rs b/gtk4/src/subclass/cell_editable.rs
index 4eca1de62d05..149d553cc56d 100644
--- a/gtk4/src/subclass/cell_editable.rs
+++ b/gtk4/src/subclass/cell_editable.rs
@@ -13,6 +13,7 @@ use crate::{ffi, prelude::*, subclass::prelude::*, CellEditable};
 pub trait CellEditableImpl: ObjectImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<CellEditable>,
 {
     fn editing_done(&self) {
         self.parent_editing_done()
@@ -32,6 +33,7 @@ where
 pub trait CellEditableImplExt: CellEditableImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<CellEditable>,
 {
     fn parent_editing_done(&self) {
         unsafe {
@@ -84,14 +86,17 @@ where
     }
 }
 
-impl<T: CellEditableImpl> CellEditableImplExt for T where
-    <T as ObjectSubclass>::Type: IsA<glib::Object>
+impl<T: CellEditableImpl> CellEditableImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellEditable>,
 {
 }
 
 unsafe impl<T: CellEditableImpl> IsImplementable<T> for CellEditable
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellEditable>,
 {
     fn interface_init(iface: &mut glib::Interface<Self>) {
         let iface = iface.as_mut();
@@ -108,6 +113,7 @@ unsafe extern "C" fn cell_editable_editing_done<T: CellEditableImpl>(
     cell_editable: *mut ffi::GtkCellEditable,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellEditable>,
 {
     let instance = &*(cell_editable as *mut T::Instance);
     let imp = instance.imp();
@@ -119,6 +125,7 @@ unsafe extern "C" fn cell_editable_remove_widget<T: CellEditableImpl>(
     cell_editable: *mut ffi::GtkCellEditable,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellEditable>,
 {
     let instance = &*(cell_editable as *mut T::Instance);
     let imp = instance.imp();
@@ -131,6 +138,7 @@ unsafe extern "C" fn cell_editable_start_editing<T: CellEditableImpl>(
     eventptr: *mut gdk::ffi::GdkEvent,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellEditable>,
 {
     let instance = &*(cell_editable as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/cell_layout.rs b/gtk4/src/subclass/cell_layout.rs
index 11b95dddf8b7..8dd2efe85c6d 100644
--- a/gtk4/src/subclass/cell_layout.rs
+++ b/gtk4/src/subclass/cell_layout.rs
@@ -56,6 +56,7 @@ impl Drop for CellLayoutDataCallback {
 pub trait CellLayoutImpl: ObjectImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<CellLayout>,
 {
     fn add_attribute<R: IsA<CellRenderer>>(&self, cell: &R, attribute: &str, column: i32) {
         self.parent_add_attribute(cell, attribute, column)
@@ -104,6 +105,7 @@ where
 pub trait CellLayoutImplExt: CellLayoutImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<CellLayout>,
 {
     fn parent_add_attribute<R: IsA<CellRenderer>>(&self, cell: &R, attribute: &str, column: i32) {
         unsafe {
@@ -268,11 +270,17 @@ where
     }
 }
 
-impl<T: CellLayoutImpl> CellLayoutImplExt for T where <T as ObjectSubclass>::Type: IsA<glib::Object> {}
+impl<T: CellLayoutImpl> CellLayoutImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellLayout>,
+{
+}
 
 unsafe impl<T: CellLayoutImpl> IsImplementable<T> for CellLayout
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellLayout>,
 {
     fn interface_init(iface: &mut glib::Interface<Self>) {
         let iface = iface.as_mut();
@@ -296,6 +304,7 @@ unsafe extern "C" fn cell_layout_get_area<T: CellLayoutImpl>(
 ) -> *mut ffi::GtkCellArea
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellLayout>,
 {
     let instance = &*(cell_layout as *mut T::Instance);
     let imp = instance.imp();
@@ -309,6 +318,7 @@ unsafe extern "C" fn cell_layout_pack_start<T: CellLayoutImpl>(
     expand: glib::ffi::gboolean,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellLayout>,
 {
     let instance = &*(cell_layout as *mut T::Instance);
     let imp = instance.imp();
@@ -323,6 +333,7 @@ unsafe extern "C" fn cell_layout_pack_end<T: CellLayoutImpl>(
     expand: glib::ffi::gboolean,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellLayout>,
 {
     let instance = &*(cell_layout as *mut T::Instance);
     let imp = instance.imp();
@@ -334,6 +345,7 @@ unsafe extern "C" fn cell_layout_pack_end<T: CellLayoutImpl>(
 unsafe extern "C" fn cell_layout_clear<T: CellLayoutImpl>(cell_layout: *mut ffi::GtkCellLayout)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellLayout>,
 {
     let instance = &*(cell_layout as *mut T::Instance);
     let imp = instance.imp();
@@ -347,6 +359,7 @@ unsafe extern "C" fn cell_layout_reorder<T: CellLayoutImpl>(
     position: i32,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellLayout>,
 {
     let instance = &*(cell_layout as *mut T::Instance);
     let imp = instance.imp();
@@ -362,6 +375,7 @@ unsafe extern "C" fn cell_layout_add_attribute<T: CellLayoutImpl>(
     column: i32,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellLayout>,
 {
     let instance = &*(cell_layout as *mut T::Instance);
     let imp = instance.imp();
@@ -376,6 +390,7 @@ unsafe extern "C" fn cell_layout_clear_attributes<T: CellLayoutImpl>(
     cellptr: *mut ffi::GtkCellRenderer,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellLayout>,
 {
     let instance = &*(cell_layout as *mut T::Instance);
     let imp = instance.imp();
@@ -392,6 +407,7 @@ unsafe extern "C" fn cell_layout_set_cell_data_func<T: CellLayoutImpl>(
     destroy_notify: glib::ffi::GDestroyNotify,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellLayout>,
 {
     let instance = &*(cell_layout as *mut T::Instance);
     let imp = instance.imp();
@@ -416,6 +432,7 @@ unsafe extern "C" fn cell_layout_get_cells<T: CellLayoutImpl>(
 ) -> *mut glib::ffi::GList
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellLayout>,
 {
     let instance = &*(cell_layout as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/cell_renderer.rs b/gtk4/src/subclass/cell_renderer.rs
index 1b04d8095aea..2a2b86180292 100644
--- a/gtk4/src/subclass/cell_renderer.rs
+++ b/gtk4/src/subclass/cell_renderer.rs
@@ -18,6 +18,7 @@ use crate::{
 pub trait CellRendererImpl: ObjectImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<CellRenderer>,
 {
     fn activate<P: IsA<Widget>>(
         &self,
@@ -103,6 +104,7 @@ where
 pub trait CellRendererImplExt: CellRendererImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<CellRenderer>,
 {
     fn parent_request_mode(&self) -> SizeRequestMode {
         unsafe {
@@ -354,14 +356,17 @@ where
     }
 }
 
-impl<T: CellRendererImpl> CellRendererImplExt for T where
-    <T as ObjectSubclass>::Type: IsA<glib::Object>
+impl<T: CellRendererImpl> CellRendererImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellRenderer>,
 {
 }
 
 unsafe impl<T: CellRendererImpl> IsSubclassable<T> for CellRenderer
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellRenderer>,
 {
     fn class_init(class: &mut ::glib::Class<Self>) {
         Self::parent_class_init::<T>(class);
@@ -397,6 +402,7 @@ unsafe extern "C" fn cell_renderer_activate<T: CellRendererImpl>(
 ) -> glib::ffi::gboolean
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellRenderer>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -418,6 +424,7 @@ unsafe extern "C" fn cell_renderer_editing_canceled<T: CellRendererImpl>(
     ptr: *mut ffi::GtkCellRenderer,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellRenderer>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -431,6 +438,7 @@ unsafe extern "C" fn cell_renderer_editing_started<T: CellRendererImpl>(
     pathptr: *const c_char,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellRenderer>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -447,6 +455,7 @@ unsafe extern "C" fn cell_renderer_get_aligned_area<T: CellRendererImpl>(
     alignedptr: *mut gdk::ffi::GdkRectangle,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellRenderer>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -464,6 +473,7 @@ unsafe extern "C" fn cell_renderer_get_preferred_height_for_width<T: CellRendere
     nat_height_ptr: *mut c_int,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellRenderer>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -485,6 +495,7 @@ unsafe extern "C" fn cell_renderer_get_preferred_height<T: CellRendererImpl>(
     natptr: *mut c_int,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellRenderer>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -507,6 +518,7 @@ unsafe extern "C" fn cell_renderer_get_preferred_width_for_height<T: CellRendere
     nat_width_ptr: *mut c_int,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellRenderer>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -528,6 +540,7 @@ unsafe extern "C" fn cell_renderer_get_preferred_width<T: CellRendererImpl>(
     natptr: *mut c_int,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellRenderer>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -547,6 +560,7 @@ unsafe extern "C" fn cell_renderer_get_request_mode<T: CellRendererImpl>(
 ) -> ffi::GtkSizeRequestMode
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellRenderer>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -563,6 +577,7 @@ unsafe extern "C" fn cell_renderer_snapshot<T: CellRendererImpl>(
     flags: ffi::GtkCellRendererState,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellRenderer>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -589,6 +604,7 @@ unsafe extern "C" fn cell_renderer_start_editing<T: CellRendererImpl>(
 ) -> *mut ffi::GtkCellEditable
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellRenderer>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/cell_renderer_text.rs b/gtk4/src/subclass/cell_renderer_text.rs
index 61e919b69b3a..caeec07e71c0 100644
--- a/gtk4/src/subclass/cell_renderer_text.rs
+++ b/gtk4/src/subclass/cell_renderer_text.rs
@@ -6,13 +6,15 @@
 
 use glib::{translate::*, GString};
 
-use crate::{ffi, prelude::*, subclass::prelude::*, CellRendererText};
+use crate::{ffi, prelude::*, subclass::prelude::*, CellRenderer, CellRendererText};
 
 #[cfg_attr(feature = "v4_10", deprecated = "Since 4.10")]
 #[allow(deprecated)]
 pub trait CellRendererTextImpl: CellRendererImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<CellRenderer>,
+    <Self as ObjectSubclass>::Type: IsA<CellRendererText>,
 {
     fn edited(&self, path: &str, new_text: &str) {
         self.parent_edited(path, new_text);
@@ -24,6 +26,8 @@ where
 pub trait CellRendererTextImplExt: CellRendererTextImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<CellRenderer>,
+    <Self as ObjectSubclass>::Type: IsA<CellRendererText>,
 {
     fn parent_edited(&self, path: &str, new_text: &str) {
         unsafe {
@@ -43,14 +47,19 @@ where
     }
 }
 
-impl<T: CellRendererTextImpl> CellRendererTextImplExt for T where
-    <T as ObjectSubclass>::Type: IsA<glib::Object>
+impl<T: CellRendererTextImpl> CellRendererTextImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellRenderer>,
+    <T as ObjectSubclass>::Type: IsA<CellRendererText>,
 {
 }
 
 unsafe impl<T: CellRendererTextImpl> IsSubclassable<T> for CellRendererText
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellRenderer>,
+    <T as ObjectSubclass>::Type: IsA<CellRendererText>,
 {
     fn class_init(class: &mut ::glib::Class<Self>) {
         Self::parent_class_init::<T>(class);
@@ -66,6 +75,8 @@ unsafe extern "C" fn cell_renderer_text_edited<T: CellRendererTextImpl>(
     new_text: *const libc::c_char,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<CellRenderer>,
+    <T as ObjectSubclass>::Type: IsA<CellRendererText>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/check_button.rs b/gtk4/src/subclass/check_button.rs
index 3c9aa667e9c4..338b05c66ca7 100644
--- a/gtk4/src/subclass/check_button.rs
+++ b/gtk4/src/subclass/check_button.rs
@@ -5,11 +5,13 @@
 
 use glib::translate::*;
 
-use crate::{ffi, prelude::*, subclass::prelude::*, CheckButton};
+use crate::{ffi, prelude::*, subclass::prelude::*, CheckButton, Widget};
 
 pub trait CheckButtonImpl: WidgetImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Widget>,
+    <Self as ObjectSubclass>::Type: IsA<CheckButton>,
 {
     fn toggled(&self) {
         self.parent_toggled()
@@ -25,6 +27,8 @@ where
 pub trait CheckButtonImplExt: CheckButtonImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Widget>,
+    <Self as ObjectSubclass>::Type: IsA<CheckButton>,
 {
     fn parent_toggled(&self) {
         unsafe {
@@ -49,14 +53,19 @@ where
     }
 }
 
-impl<T: CheckButtonImpl> CheckButtonImplExt for T where
-    <T as ObjectSubclass>::Type: IsA<glib::Object>
+impl<T: CheckButtonImpl> CheckButtonImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<CheckButton>,
 {
 }
 
 unsafe impl<T: CheckButtonImpl> IsSubclassable<T> for CheckButton
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<CheckButton>,
 {
     fn class_init(class: &mut glib::Class<Self>) {
         Self::parent_class_init::<T>(class);
@@ -75,6 +84,8 @@ where
 unsafe extern "C" fn check_button_toggled<T: CheckButtonImpl>(ptr: *mut ffi::GtkCheckButton)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<CheckButton>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -87,6 +98,8 @@ where
 unsafe extern "C" fn check_button_activate<T: CheckButtonImpl>(ptr: *mut ffi::GtkCheckButton)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<CheckButton>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/color_chooser.rs b/gtk4/src/subclass/color_chooser.rs
index f15f5ee574c3..c44e4d323298 100644
--- a/gtk4/src/subclass/color_chooser.rs
+++ b/gtk4/src/subclass/color_chooser.rs
@@ -14,6 +14,7 @@ use crate::{ffi, prelude::*, subclass::prelude::*, ColorChooser, Orientation};
 pub trait ColorChooserImpl: ObjectImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<ColorChooser>,
 {
     fn add_palette(&self, orientation: Orientation, colors_per_line: i32, colors: &[RGBA]) {
         self.parent_add_palette(orientation, colors_per_line, colors);
@@ -33,6 +34,7 @@ where
 pub trait ColorChooserImplExt: ColorChooserImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<ColorChooser>,
 {
     fn parent_add_palette(&self, orientation: Orientation, colors_per_line: i32, colors: &[RGBA]) {
         unsafe {
@@ -116,14 +118,17 @@ where
     }
 }
 
-impl<T: ColorChooserImpl> ColorChooserImplExt for T where
-    <T as ObjectSubclass>::Type: IsA<glib::Object>
+impl<T: ColorChooserImpl> ColorChooserImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<ColorChooser>,
 {
 }
 
 unsafe impl<T: ColorChooserImpl> IsImplementable<T> for ColorChooser
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<ColorChooser>,
 {
     fn interface_init(iface: &mut glib::Interface<Self>) {
         let iface = iface.as_mut();
@@ -145,6 +150,7 @@ unsafe extern "C" fn color_chooser_add_palette<T: ColorChooserImpl>(
     colorsptr: *mut gdk::ffi::GdkRGBA,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<ColorChooser>,
 {
     let instance = &*(color_chooser as *mut T::Instance);
     let imp = instance.imp();
@@ -162,6 +168,7 @@ unsafe extern "C" fn color_chooser_color_activated<T: ColorChooserImpl>(
     rgba: *const gdk::ffi::GdkRGBA,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<ColorChooser>,
 {
     let instance = &*(color_chooser as *mut T::Instance);
     let imp = instance.imp();
@@ -174,6 +181,7 @@ unsafe extern "C" fn color_chooser_get_rgba<T: ColorChooserImpl>(
     rgbaptr: *const gdk::ffi::GdkRGBA,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<ColorChooser>,
 {
     let instance = &*(color_chooser as *mut T::Instance);
     let imp = instance.imp();
@@ -187,6 +195,7 @@ unsafe extern "C" fn color_chooser_set_rgba<T: ColorChooserImpl>(
     rgba: *const gdk::ffi::GdkRGBA,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<ColorChooser>,
 {
     let instance = &*(color_chooser as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/combo_box.rs b/gtk4/src/subclass/combo_box.rs
index 0ed7888f7b91..0429474bae7b 100644
--- a/gtk4/src/subclass/combo_box.rs
+++ b/gtk4/src/subclass/combo_box.rs
@@ -5,13 +5,15 @@
 
 use glib::{translate::*, GString};
 
-use crate::{ffi, prelude::*, subclass::prelude::*, ComboBox};
+use crate::{ffi, prelude::*, subclass::prelude::*, ComboBox, Widget};
 
 #[cfg_attr(feature = "v4_10", deprecated = "Since 4.10")]
 #[allow(deprecated)]
 pub trait ComboBoxImpl: WidgetImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Widget>,
+    <Self as ObjectSubclass>::Type: IsA<ComboBox>,
 {
     #[cfg(feature = "v4_6")]
     #[cfg_attr(docsrs, doc(cfg(feature = "v4_6")))]
@@ -31,6 +33,8 @@ where
 pub trait ComboBoxImplExt: ComboBoxImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Widget>,
+    <Self as ObjectSubclass>::Type: IsA<ComboBox>,
 {
     #[cfg(feature = "v4_6")]
     #[cfg_attr(docsrs, doc(cfg(feature = "v4_6")))]
@@ -67,11 +71,19 @@ where
     }
 }
 
-impl<T: ComboBoxImpl> ComboBoxImplExt for T where <T as ObjectSubclass>::Type: IsA<glib::Object> {}
+impl<T: ComboBoxImpl> ComboBoxImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<ComboBox>,
+{
+}
 
 unsafe impl<T: ComboBoxImpl> IsSubclassable<T> for ComboBox
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<ComboBox>,
 {
     fn class_init(class: &mut glib::Class<Self>) {
         Self::parent_class_init::<T>(class);
@@ -90,6 +102,8 @@ where
 unsafe extern "C" fn combo_box_changed<T: ComboBoxImpl>(ptr: *mut ffi::GtkComboBox)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<ComboBox>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -103,6 +117,8 @@ unsafe extern "C" fn combo_box_format_entry_text<T: ComboBoxImpl>(
 ) -> *mut libc::c_char
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<ComboBox>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -116,6 +132,8 @@ where
 unsafe extern "C" fn combo_box_activate<T: ComboBoxImpl>(ptr: *mut ffi::GtkComboBox)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<ComboBox>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/dialog.rs b/gtk4/src/subclass/dialog.rs
index fed0755688b1..b127a1d7825f 100644
--- a/gtk4/src/subclass/dialog.rs
+++ b/gtk4/src/subclass/dialog.rs
@@ -5,11 +5,14 @@
 
 use glib::translate::*;
 
-use crate::{ffi, prelude::*, subclass::prelude::*, Dialog, ResponseType};
+use crate::{ffi, prelude::*, subclass::prelude::*, Dialog, ResponseType, Widget, Window};
 
 pub trait DialogImpl: WindowImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Widget>,
+    <Self as ObjectSubclass>::Type: IsA<Window>,
+    <Self as ObjectSubclass>::Type: IsA<Dialog>,
 {
     fn response(&self, response: ResponseType) {
         self.parent_response(response)
@@ -23,6 +26,9 @@ where
 pub trait DialogImplExt: DialogImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Widget>,
+    <Self as ObjectSubclass>::Type: IsA<Window>,
+    <Self as ObjectSubclass>::Type: IsA<Dialog>,
 {
     fn parent_response(&self, response: ResponseType) {
         unsafe {
@@ -48,11 +54,21 @@ where
     }
 }
 
-impl<T: DialogImpl> DialogImplExt for T where <T as ObjectSubclass>::Type: IsA<glib::Object> {}
+impl<T: DialogImpl> DialogImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Window>,
+    <T as ObjectSubclass>::Type: IsA<Dialog>,
+{
+}
 
 unsafe impl<T: DialogImpl> IsSubclassable<T> for Dialog
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Window>,
+    <T as ObjectSubclass>::Type: IsA<Dialog>,
 {
     fn class_init(class: &mut glib::Class<Self>) {
         Self::parent_class_init::<T>(class);
@@ -66,6 +82,9 @@ where
 unsafe extern "C" fn dialog_response<T: DialogImpl>(ptr: *mut ffi::GtkDialog, responseptr: i32)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Window>,
+    <T as ObjectSubclass>::Type: IsA<Dialog>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -77,6 +96,9 @@ where
 unsafe extern "C" fn dialog_close<T: DialogImpl>(ptr: *mut ffi::GtkDialog)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Window>,
+    <T as ObjectSubclass>::Type: IsA<Dialog>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/drawing_area.rs b/gtk4/src/subclass/drawing_area.rs
index 9cb4a2175533..b5ce630698ea 100644
--- a/gtk4/src/subclass/drawing_area.rs
+++ b/gtk4/src/subclass/drawing_area.rs
@@ -5,11 +5,13 @@
 
 use glib::translate::*;
 
-use crate::{ffi, prelude::*, subclass::prelude::*, DrawingArea};
+use crate::{ffi, prelude::*, subclass::prelude::*, DrawingArea, Widget};
 
 pub trait DrawingAreaImpl: WidgetImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Widget>,
+    <Self as ObjectSubclass>::Type: IsA<DrawingArea>,
 {
     fn resize(&self, width: i32, height: i32) {
         self.parent_resize(width, height)
@@ -19,6 +21,8 @@ where
 pub trait DrawingAreaImplExt: DrawingAreaImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Widget>,
+    <Self as ObjectSubclass>::Type: IsA<DrawingArea>,
 {
     fn parent_resize(&self, width: i32, height: i32) {
         unsafe {
@@ -35,14 +39,19 @@ where
     }
 }
 
-impl<T: DrawingAreaImpl> DrawingAreaImplExt for T where
-    <T as ObjectSubclass>::Type: IsA<glib::Object>
+impl<T: DrawingAreaImpl> DrawingAreaImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<DrawingArea>,
 {
 }
 
 unsafe impl<T: DrawingAreaImpl> IsSubclassable<T> for DrawingArea
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<DrawingArea>,
 {
     fn class_init(class: &mut glib::Class<Self>) {
         Self::parent_class_init::<T>(class);
@@ -58,6 +67,8 @@ unsafe extern "C" fn drawing_area_resize<T: DrawingAreaImpl>(
     height: i32,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<DrawingArea>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/editable.rs b/gtk4/src/subclass/editable.rs
index e4a91ec80783..7049b6837237 100644
--- a/gtk4/src/subclass/editable.rs
+++ b/gtk4/src/subclass/editable.rs
@@ -8,11 +8,13 @@ use std::sync::OnceLock;
 use glib::{translate::*, GString, Quark};
 use libc::{c_char, c_int};
 
-use crate::{ffi, prelude::*, subclass::prelude::*, Editable};
+use crate::{ffi, prelude::*, subclass::prelude::*, Editable, Widget};
 
 pub trait EditableImpl: WidgetImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Widget>,
+    <Self as ObjectSubclass>::Type: IsA<Editable>,
 {
     fn insert_text(&self, text: &str, length: i32, position: &mut i32) {
         self.parent_insert_text(text, length, position);
@@ -57,6 +59,8 @@ where
 pub trait EditableImplExt: EditableImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Widget>,
+    <Self as ObjectSubclass>::Type: IsA<Editable>,
 {
     #[doc(alias = "gtk_editable_delegate_get_property")]
     fn delegate_get_property(
@@ -248,11 +252,19 @@ where
     }
 }
 
-impl<T: EditableImpl> EditableImplExt for T where <T as ObjectSubclass>::Type: IsA<glib::Object> {}
+impl<T: EditableImpl> EditableImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Editable>,
+{
+}
 
 unsafe impl<T: EditableImpl + ObjectSubclass> IsImplementable<T> for Editable
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Editable>,
 {
     fn interface_init(iface: &mut glib::Interface<Self>) {
         let instance_type = iface.instance_type();
@@ -292,6 +304,8 @@ unsafe extern "C" fn editable_insert_text<T: EditableImpl>(
     position: *mut c_int,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Editable>,
 {
     let instance = &*(editable as *mut T::Instance);
     let imp = instance.imp();
@@ -305,6 +319,8 @@ unsafe extern "C" fn editable_delete_text<T: EditableImpl>(
     end_position: c_int,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Editable>,
 {
     let instance = &*(editable as *mut T::Instance);
     let imp = instance.imp();
@@ -315,6 +331,8 @@ unsafe extern "C" fn editable_delete_text<T: EditableImpl>(
 unsafe extern "C" fn editable_changed<T: EditableImpl>(editable: *mut ffi::GtkEditable)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Editable>,
 {
     let instance = &*(editable as *mut T::Instance);
     let imp = instance.imp();
@@ -327,6 +345,8 @@ unsafe extern "C" fn editable_get_text<T: EditableImpl>(
 ) -> *const c_char
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Editable>,
 {
     let instance = &*(editable as *mut T::Instance);
     let imp = instance.imp();
@@ -339,6 +359,8 @@ unsafe extern "C" fn editable_get_delegate<T: EditableImpl>(
 ) -> *mut ffi::GtkEditable
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Editable>,
 {
     let instance = &*(editable as *mut T::Instance);
     let imp = instance.imp();
@@ -370,6 +392,8 @@ unsafe extern "C" fn editable_do_insert_text<T: EditableImpl>(
     position: *mut i32,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Editable>,
 {
     let instance = &*(editable as *mut T::Instance);
     let imp = instance.imp();
@@ -383,6 +407,8 @@ unsafe extern "C" fn editable_do_delete_text<T: EditableImpl>(
     end_position: i32,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Editable>,
 {
     let instance = &*(editable as *mut T::Instance);
     let imp = instance.imp();
@@ -397,6 +423,8 @@ unsafe extern "C" fn editable_get_selection_bounds<T: EditableImpl>(
 ) -> glib::ffi::gboolean
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Editable>,
 {
     let instance = &*(editable as *mut T::Instance);
     let imp = instance.imp();
@@ -423,6 +451,8 @@ unsafe extern "C" fn editable_set_selection_bounds<T: EditableImpl>(
     end_position: i32,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Editable>,
 {
     let instance = &*(editable as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/entry.rs b/gtk4/src/subclass/entry.rs
index b2f74aedd0fb..be06a63aa220 100644
--- a/gtk4/src/subclass/entry.rs
+++ b/gtk4/src/subclass/entry.rs
@@ -5,11 +5,13 @@
 
 use glib::translate::*;
 
-use crate::{ffi, prelude::*, subclass::prelude::*, Entry};
+use crate::{ffi, prelude::*, subclass::prelude::*, Entry, Widget};
 
 pub trait EntryImpl: WidgetImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Widget>,
+    <Self as ObjectSubclass>::Type: IsA<Entry>,
 {
     fn activate(&self) {
         self.parent_activate()
@@ -19,6 +21,8 @@ where
 pub trait EntryImplExt: EntryImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Widget>,
+    <Self as ObjectSubclass>::Type: IsA<Entry>,
 {
     fn parent_activate(&self) {
         unsafe {
@@ -31,11 +35,19 @@ where
     }
 }
 
-impl<T: EntryImpl> EntryImplExt for T where <T as ObjectSubclass>::Type: IsA<glib::Object> {}
+impl<T: EntryImpl> EntryImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Entry>,
+{
+}
 
 unsafe impl<T: EntryImpl> IsSubclassable<T> for Entry
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Entry>,
 {
     fn class_init(class: &mut glib::Class<Self>) {
         Self::parent_class_init::<T>(class);
@@ -48,6 +60,8 @@ where
 unsafe extern "C" fn entry_activate<T: EntryImpl>(ptr: *mut ffi::GtkEntry)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Entry>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/entry_buffer.rs b/gtk4/src/subclass/entry_buffer.rs
index b7ccbcd65f68..3d5fc266308c 100644
--- a/gtk4/src/subclass/entry_buffer.rs
+++ b/gtk4/src/subclass/entry_buffer.rs
@@ -12,6 +12,7 @@ use crate::{ffi, prelude::*, subclass::prelude::*, EntryBuffer};
 pub trait EntryBufferImpl: ObjectImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<EntryBuffer>,
 {
     fn delete_text(&self, position: u32, n_chars: Option<u32>) -> u32 {
         self.parent_delete_text(position, n_chars)
@@ -42,6 +43,7 @@ where
 pub trait EntryBufferImplExt: EntryBufferImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<EntryBuffer>,
 {
     fn parent_delete_text(&self, position: u32, n_chars: Option<u32>) -> u32 {
         unsafe {
@@ -132,14 +134,17 @@ where
     }
 }
 
-impl<T: EntryBufferImpl> EntryBufferImplExt for T where
-    <T as ObjectSubclass>::Type: IsA<glib::Object>
+impl<T: EntryBufferImpl> EntryBufferImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<EntryBuffer>,
 {
 }
 
 unsafe impl<T: EntryBufferImpl> IsSubclassable<T> for EntryBuffer
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<EntryBuffer>,
 {
     fn class_init(class: &mut glib::Class<Self>) {
         Self::parent_class_init::<T>(class);
@@ -163,6 +168,7 @@ unsafe extern "C" fn entry_buffer_delete_text<T: EntryBufferImpl>(
 ) -> u32
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<EntryBuffer>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -182,6 +188,7 @@ unsafe extern "C" fn entry_buffer_deleted_text<T: EntryBufferImpl>(
     n_chars: u32,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<EntryBuffer>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -201,6 +208,7 @@ unsafe extern "C" fn entry_buffer_get_text<T: EntryBufferImpl>(
 ) -> *const libc::c_char
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<EntryBuffer>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -230,6 +238,7 @@ unsafe extern "C" fn entry_buffer_get_length<T: EntryBufferImpl>(
 ) -> u32
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<EntryBuffer>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -245,6 +254,7 @@ unsafe extern "C" fn entry_buffer_insert_text<T: EntryBufferImpl>(
 ) -> u32
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<EntryBuffer>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -261,6 +271,7 @@ unsafe extern "C" fn entry_buffer_inserted_text<T: EntryBufferImpl>(
     length: u32,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<EntryBuffer>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/filter.rs b/gtk4/src/subclass/filter.rs
index a0c91c49baa5..c4004e0401a2 100644
--- a/gtk4/src/subclass/filter.rs
+++ b/gtk4/src/subclass/filter.rs
@@ -10,6 +10,7 @@ use crate::{ffi, prelude::*, subclass::prelude::*, Filter, FilterMatch};
 pub trait FilterImpl: ObjectImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Filter>,
 {
     #[doc(alias = "get_strictness")]
     fn strictness(&self) -> FilterMatch {
@@ -23,6 +24,7 @@ where
 pub trait FilterImplExt: FilterImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Filter>,
 {
     fn parent_strictness(&self) -> FilterMatch {
         unsafe {
@@ -50,11 +52,17 @@ where
     }
 }
 
-impl<T: FilterImpl> FilterImplExt for T where <T as ObjectSubclass>::Type: IsA<glib::Object> {}
+impl<T: FilterImpl> FilterImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Filter>,
+{
+}
 
 unsafe impl<T: FilterImpl> IsSubclassable<T> for Filter
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Filter>,
 {
     fn class_init(class: &mut glib::Class<Self>) {
         Self::parent_class_init::<T>(class);
@@ -72,6 +80,7 @@ unsafe extern "C" fn filter_get_strictness<T: FilterImpl>(
 ) -> ffi::GtkFilterMatch
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Filter>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -85,6 +94,7 @@ unsafe extern "C" fn filter_match<T: FilterImpl>(
 ) -> glib::ffi::gboolean
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Filter>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/fixed.rs b/gtk4/src/subclass/fixed.rs
index 0d97f9259e1a..3e717fef4398 100644
--- a/gtk4/src/subclass/fixed.rs
+++ b/gtk4/src/subclass/fixed.rs
@@ -3,15 +3,20 @@
 // rustdoc-stripper-ignore-next
 //! Traits intended for subclassing [`Fixed`](crate::Fixed).
 
-use crate::{prelude::*, subclass::prelude::*, Fixed};
+use crate::{prelude::*, subclass::prelude::*, Fixed, Widget};
 
 pub trait FixedImpl: WidgetImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Widget>,
+    <Self as ObjectSubclass>::Type: IsA<Fixed>,
 {
 }
 
-unsafe impl<T: FixedImpl> IsSubclassable<T> for Fixed where
-    <T as ObjectSubclass>::Type: IsA<glib::Object>
+unsafe impl<T: FixedImpl> IsSubclassable<T> for Fixed
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Fixed>,
 {
 }
diff --git a/gtk4/src/subclass/flow_box_child.rs b/gtk4/src/subclass/flow_box_child.rs
index 703351656c1e..6511c39ff3d1 100644
--- a/gtk4/src/subclass/flow_box_child.rs
+++ b/gtk4/src/subclass/flow_box_child.rs
@@ -5,11 +5,13 @@
 
 use glib::translate::*;
 
-use crate::{ffi, prelude::*, subclass::prelude::*, FlowBoxChild};
+use crate::{ffi, prelude::*, subclass::prelude::*, FlowBoxChild, Widget};
 
 pub trait FlowBoxChildImpl: WidgetImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Widget>,
+    <Self as ObjectSubclass>::Type: IsA<FlowBoxChild>,
 {
     fn activate(&self) {
         self.parent_activate()
@@ -19,6 +21,8 @@ where
 pub trait FlowBoxChildImplExt: FlowBoxChildImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Widget>,
+    <Self as ObjectSubclass>::Type: IsA<FlowBoxChild>,
 {
     fn parent_activate(&self) {
         unsafe {
@@ -35,14 +39,19 @@ where
     }
 }
 
-impl<T: FlowBoxChildImpl> FlowBoxChildImplExt for T where
-    <T as ObjectSubclass>::Type: IsA<glib::Object>
+impl<T: FlowBoxChildImpl> FlowBoxChildImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<FlowBoxChild>,
 {
 }
 
 unsafe impl<T: FlowBoxChildImpl> IsSubclassable<T> for FlowBoxChild
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<FlowBoxChild>,
 {
     fn class_init(class: &mut glib::Class<Self>) {
         Self::parent_class_init::<T>(class);
@@ -55,6 +64,8 @@ where
 unsafe extern "C" fn child_activate<T: FlowBoxChildImpl>(ptr: *mut ffi::GtkFlowBoxChild)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<FlowBoxChild>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/font_chooser.rs b/gtk4/src/subclass/font_chooser.rs
index 1a96db52b51a..359d19fc3d11 100644
--- a/gtk4/src/subclass/font_chooser.rs
+++ b/gtk4/src/subclass/font_chooser.rs
@@ -52,6 +52,7 @@ impl Drop for FilterCallback {
 pub trait FontChooserImpl: ObjectImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<FontChooser>,
 {
     fn font_family(&self) -> Option<FontFamily> {
         self.parent_font_family()
@@ -87,6 +88,7 @@ where
 pub trait FontChooserImplExt: FontChooserImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<FontChooser>,
 {
     fn parent_font_family(&self) -> Option<FontFamily> {
         unsafe {
@@ -213,14 +215,17 @@ where
     }
 }
 
-impl<T: FontChooserImpl> FontChooserImplExt for T where
-    <T as ObjectSubclass>::Type: IsA<glib::Object>
+impl<T: FontChooserImpl> FontChooserImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<FontChooser>,
 {
 }
 
 unsafe impl<T: FontChooserImpl> IsImplementable<T> for FontChooser
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<FontChooser>,
 {
     fn interface_init(iface: &mut glib::Interface<Self>) {
         let iface = iface.as_mut();
@@ -242,6 +247,7 @@ unsafe extern "C" fn font_chooser_get_font_family<T: FontChooserImpl>(
 ) -> *mut pango::ffi::PangoFontFamily
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<FontChooser>,
 {
     let instance = &*(font_chooser as *mut T::Instance);
     let imp = instance.imp();
@@ -271,6 +277,7 @@ unsafe extern "C" fn font_chooser_get_font_face<T: FontChooserImpl>(
 ) -> *mut pango::ffi::PangoFontFace
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<FontChooser>,
 {
     let instance = &*(font_chooser as *mut T::Instance);
     let imp = instance.imp();
@@ -298,6 +305,7 @@ unsafe extern "C" fn font_chooser_get_font_size<T: FontChooserImpl>(
 ) -> i32
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<FontChooser>,
 {
     let instance = &*(font_chooser as *mut T::Instance);
     let imp = instance.imp();
@@ -310,6 +318,7 @@ unsafe extern "C" fn font_chooser_font_activated<T: FontChooserImpl>(
     font_nameptr: *const libc::c_char,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<FontChooser>,
 {
     let instance = &*(font_chooser as *mut T::Instance);
     let imp = instance.imp();
@@ -323,6 +332,7 @@ unsafe extern "C" fn font_chooser_set_font_map<T: FontChooserImpl>(
     font_mapptr: *mut pango::ffi::PangoFontMap,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<FontChooser>,
 {
     let instance = &*(font_chooser as *mut T::Instance);
     let imp = instance.imp();
@@ -336,6 +346,7 @@ unsafe extern "C" fn font_chooser_get_font_map<T: FontChooserImpl>(
 ) -> *mut pango::ffi::PangoFontMap
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<FontChooser>,
 {
     let instance = &*(font_chooser as *mut T::Instance);
     let imp = instance.imp();
@@ -350,6 +361,7 @@ unsafe extern "C" fn font_chooser_set_filter_func<T: FontChooserImpl>(
     destroy_notify: glib::ffi::GDestroyNotify,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<FontChooser>,
 {
     let instance = &*(font_chooser as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/frame.rs b/gtk4/src/subclass/frame.rs
index 6285db2a5547..5fe37b980f6b 100644
--- a/gtk4/src/subclass/frame.rs
+++ b/gtk4/src/subclass/frame.rs
@@ -5,13 +5,15 @@
 
 use glib::translate::*;
 
-use crate::{ffi, prelude::*, subclass::prelude::*, Allocation, Frame};
+use crate::{ffi, prelude::*, subclass::prelude::*, Allocation, Frame, Widget};
 
 #[cfg_attr(feature = "v4_10", deprecated = "Since 4.10")]
 #[allow(deprecated)]
 pub trait FrameImpl: WidgetImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Widget>,
+    <Self as ObjectSubclass>::Type: IsA<Frame>,
 {
     fn compute_child_allocation(&self) -> Allocation {
         self.parent_compute_child_allocation()
@@ -23,6 +25,8 @@ where
 pub trait FrameImplExt: FrameImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Widget>,
+    <Self as ObjectSubclass>::Type: IsA<Frame>,
 {
     fn parent_compute_child_allocation(&self) -> Allocation {
         unsafe {
@@ -41,11 +45,19 @@ where
     }
 }
 
-impl<T: FrameImpl> FrameImplExt for T where <T as ObjectSubclass>::Type: IsA<glib::Object> {}
+impl<T: FrameImpl> FrameImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Frame>,
+{
+}
 
 unsafe impl<T: FrameImpl> IsSubclassable<T> for Frame
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Frame>,
 {
     fn class_init(class: &mut glib::Class<Self>) {
         Self::parent_class_init::<T>(class);
@@ -60,6 +72,8 @@ unsafe extern "C" fn frame_compute_child_allocation<T: FrameImpl>(
     allocationptr: *mut ffi::GtkAllocation,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Frame>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/gl_area.rs b/gtk4/src/subclass/gl_area.rs
index 85d316d7da5d..2f9affc6e86d 100644
--- a/gtk4/src/subclass/gl_area.rs
+++ b/gtk4/src/subclass/gl_area.rs
@@ -6,12 +6,14 @@
 use gdk::GLContext;
 use glib::translate::*;
 
-use crate::{ffi, prelude::*, subclass::prelude::*, GLArea};
+use crate::{ffi, prelude::*, subclass::prelude::*, GLArea, Widget};
 
 #[allow(clippy::upper_case_acronyms)]
 pub trait GLAreaImpl: WidgetImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Widget>,
+    <Self as ObjectSubclass>::Type: IsA<GLArea>,
 {
     fn create_context(&self) -> Option<GLContext> {
         self.parent_create_context()
@@ -30,6 +32,8 @@ where
 pub trait GLAreaImplExt: GLAreaImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Widget>,
+    <Self as ObjectSubclass>::Type: IsA<GLArea>,
 {
     fn parent_create_context(&self) -> Option<GLContext> {
         unsafe {
@@ -75,11 +79,19 @@ where
     }
 }
 
-impl<T: GLAreaImpl> GLAreaImplExt for T where <T as ObjectSubclass>::Type: IsA<glib::Object> {}
+impl<T: GLAreaImpl> GLAreaImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<GLArea>,
+{
+}
 
 unsafe impl<T: GLAreaImpl> IsSubclassable<T> for GLArea
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<GLArea>,
 {
     fn class_init(class: &mut glib::Class<Self>) {
         Self::parent_class_init::<T>(class);
@@ -96,6 +108,8 @@ unsafe extern "C" fn gl_area_create_context<T: GLAreaImpl>(
 ) -> *mut gdk::ffi::GdkGLContext
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<GLArea>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -109,6 +123,8 @@ unsafe extern "C" fn gl_area_render<T: GLAreaImpl>(
 ) -> glib::ffi::gboolean
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<GLArea>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -122,6 +138,8 @@ unsafe extern "C" fn gl_area_resize<T: GLAreaImpl>(
     height: i32,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<GLArea>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/grid.rs b/gtk4/src/subclass/grid.rs
index 93ab4909b2bc..fdc137bb6b95 100644
--- a/gtk4/src/subclass/grid.rs
+++ b/gtk4/src/subclass/grid.rs
@@ -3,15 +3,20 @@
 // rustdoc-stripper-ignore-next
 //! Traits intended for subclassing [`Grid`](crate::Grid).
 
-use crate::{prelude::*, subclass::prelude::*, Grid};
+use crate::{prelude::*, subclass::prelude::*, Grid, Widget};
 
 pub trait GridImpl: WidgetImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Widget>,
+    <Self as ObjectSubclass>::Type: IsA<Grid>,
 {
 }
 
-unsafe impl<T: GridImpl> IsSubclassable<T> for Grid where
-    <T as ObjectSubclass>::Type: IsA<glib::Object>
+unsafe impl<T: GridImpl> IsSubclassable<T> for Grid
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Grid>,
 {
 }
diff --git a/gtk4/src/subclass/im_context.rs b/gtk4/src/subclass/im_context.rs
index adf83406ed3d..c34e100b38dc 100644
--- a/gtk4/src/subclass/im_context.rs
+++ b/gtk4/src/subclass/im_context.rs
@@ -12,6 +12,7 @@ use crate::{ffi, prelude::*, subclass::prelude::*, IMContext, Widget};
 pub trait IMContextImpl: ObjectImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<IMContext>,
 {
     fn commit(&self, string: &str) {
         self.parent_commit(string)
@@ -81,6 +82,7 @@ where
 pub trait IMContextImplExt: IMContextImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<IMContext>,
 {
     fn parent_commit(&self, string: &str) {
         unsafe {
@@ -335,11 +337,17 @@ where
     }
 }
 
-impl<T: IMContextImpl> IMContextImplExt for T where <T as ObjectSubclass>::Type: IsA<glib::Object> {}
+impl<T: IMContextImpl> IMContextImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<IMContext>,
+{
+}
 
 unsafe impl<T: IMContextImpl> IsSubclassable<T> for IMContext
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<IMContext>,
 {
     fn class_init(class: &mut glib::Class<Self>) {
         Self::parent_class_init::<T>(class);
@@ -381,6 +389,7 @@ unsafe extern "C" fn im_context_commit<T: IMContextImpl>(
     stringptr: *const libc::c_char,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<IMContext>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -396,6 +405,7 @@ unsafe extern "C" fn im_context_delete_surrounding<T: IMContextImpl>(
 ) -> glib::ffi::gboolean
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<IMContext>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -409,6 +419,7 @@ unsafe extern "C" fn im_context_filter_keypress<T: IMContextImpl>(
 ) -> glib::ffi::gboolean
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<IMContext>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -419,6 +430,7 @@ where
 unsafe extern "C" fn im_context_focus_in<T: IMContextImpl>(ptr: *mut ffi::GtkIMContext)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<IMContext>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -429,6 +441,7 @@ where
 unsafe extern "C" fn im_context_focus_out<T: IMContextImpl>(ptr: *mut ffi::GtkIMContext)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<IMContext>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -443,6 +456,7 @@ unsafe extern "C" fn im_context_get_preedit_string<T: IMContextImpl>(
     cursor_index_ptr: *mut libc::c_int,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<IMContext>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -461,6 +475,7 @@ unsafe extern "C" fn im_context_get_surrounding<T: IMContextImpl>(
 ) -> glib::ffi::gboolean
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<IMContext>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -479,6 +494,7 @@ where
 unsafe extern "C" fn im_context_preedit_changed<T: IMContextImpl>(ptr: *mut ffi::GtkIMContext)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<IMContext>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -489,6 +505,7 @@ where
 unsafe extern "C" fn im_context_preedit_end<T: IMContextImpl>(ptr: *mut ffi::GtkIMContext)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<IMContext>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -499,6 +516,7 @@ where
 unsafe extern "C" fn im_context_preedit_start<T: IMContextImpl>(ptr: *mut ffi::GtkIMContext)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<IMContext>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -509,6 +527,7 @@ where
 unsafe extern "C" fn im_context_reset<T: IMContextImpl>(ptr: *mut ffi::GtkIMContext)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<IMContext>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -521,6 +540,7 @@ unsafe extern "C" fn im_context_retrieve_surrounding<T: IMContextImpl>(
 ) -> glib::ffi::gboolean
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<IMContext>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -533,6 +553,7 @@ unsafe extern "C" fn im_context_set_client_widget<T: IMContextImpl>(
     widgetptr: *mut ffi::GtkWidget,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<IMContext>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -546,6 +567,7 @@ unsafe extern "C" fn im_context_set_cursor_location<T: IMContextImpl>(
     areaptr: *mut gdk::ffi::GdkRectangle,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<IMContext>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -561,6 +583,7 @@ unsafe extern "C" fn im_context_set_surrounding<T: IMContextImpl>(
     cursor_index: i32,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<IMContext>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -581,6 +604,7 @@ unsafe extern "C" fn im_context_set_use_preedit<T: IMContextImpl>(
     use_preedit: glib::ffi::gboolean,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<IMContext>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -593,6 +617,7 @@ unsafe extern "C" fn im_context_set_use_preedit<T: IMContextImpl>(
 unsafe extern "C" fn im_context_activate_osk<T: IMContextImpl>(ptr: *mut ffi::GtkIMContext)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<IMContext>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -608,6 +633,7 @@ unsafe extern "C" fn im_context_activate_osk_with_event<T: IMContextImpl>(
 ) -> glib::ffi::gboolean
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<IMContext>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/layout_child.rs b/gtk4/src/subclass/layout_child.rs
index 681af0ed7fcd..d36bdcf860ed 100644
--- a/gtk4/src/subclass/layout_child.rs
+++ b/gtk4/src/subclass/layout_child.rs
@@ -8,12 +8,14 @@ use crate::{prelude::*, subclass::prelude::*, LayoutChild};
 pub trait LayoutChildImpl: ObjectImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<LayoutChild>,
 {
 }
 
 unsafe impl<T: LayoutChildImpl> IsSubclassable<T> for LayoutChild
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<LayoutChild>,
 {
     fn class_init(class: &mut glib::Class<Self>) {
         Self::parent_class_init::<T>(class);
diff --git a/gtk4/src/subclass/layout_manager.rs b/gtk4/src/subclass/layout_manager.rs
index d794c165325f..2896604e110a 100644
--- a/gtk4/src/subclass/layout_manager.rs
+++ b/gtk4/src/subclass/layout_manager.rs
@@ -14,6 +14,7 @@ use crate::{
 pub trait LayoutManagerImpl: ObjectImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<LayoutManager>,
 {
     fn allocate(&self, widget: &Widget, width: i32, height: i32, baseline: i32) {
         self.parent_allocate(widget, width, height, baseline)
@@ -54,6 +55,7 @@ where
 pub trait LayoutManagerImplExt: LayoutManagerImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<LayoutManager>,
 {
     fn parent_allocate(&self, widget: &Widget, width: i32, height: i32, baseline: i32) {
         unsafe {
@@ -172,14 +174,17 @@ where
     }
 }
 
-impl<T: LayoutManagerImpl> LayoutManagerImplExt for T where
-    <T as ObjectSubclass>::Type: IsA<glib::Object>
+impl<T: LayoutManagerImpl> LayoutManagerImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<LayoutManager>,
 {
 }
 
 unsafe impl<T: LayoutManagerImpl> IsSubclassable<T> for LayoutManager
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<LayoutManager>,
 {
     fn class_init(class: &mut glib::Class<Self>) {
         Self::parent_class_init::<T>(class);
@@ -207,6 +212,7 @@ unsafe extern "C" fn layout_manager_allocate<T: LayoutManagerImpl>(
     baseline: i32,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<LayoutManager>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -223,6 +229,7 @@ unsafe extern "C" fn layout_manager_create_layout_child<T: LayoutManagerImpl>(
 ) -> *mut ffi::GtkLayoutChild
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<LayoutManager>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -238,6 +245,7 @@ unsafe extern "C" fn layout_manager_get_request_mode<T: LayoutManagerImpl>(
 ) -> ffi::GtkSizeRequestMode
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<LayoutManager>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -257,6 +265,7 @@ unsafe extern "C" fn layout_manager_measure<T: LayoutManagerImpl>(
     natural_baseline_ptr: *mut c_int,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<LayoutManager>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -281,6 +290,7 @@ unsafe extern "C" fn layout_manager_measure<T: LayoutManagerImpl>(
 unsafe extern "C" fn layout_manager_root<T: LayoutManagerImpl>(ptr: *mut ffi::GtkLayoutManager)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<LayoutManager>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -291,6 +301,7 @@ where
 unsafe extern "C" fn layout_manager_unroot<T: LayoutManagerImpl>(ptr: *mut ffi::GtkLayoutManager)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<LayoutManager>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/list_box_row.rs b/gtk4/src/subclass/list_box_row.rs
index 35b4aaf1854f..43a1123564d0 100644
--- a/gtk4/src/subclass/list_box_row.rs
+++ b/gtk4/src/subclass/list_box_row.rs
@@ -5,11 +5,13 @@
 
 use glib::translate::*;
 
-use crate::{ffi, prelude::*, subclass::prelude::*, ListBoxRow};
+use crate::{ffi, prelude::*, subclass::prelude::*, ListBoxRow, Widget};
 
 pub trait ListBoxRowImpl: WidgetImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Widget>,
+    <Self as ObjectSubclass>::Type: IsA<ListBoxRow>,
 {
     fn activate(&self) {
         self.parent_activate()
@@ -19,6 +21,8 @@ where
 pub trait ListBoxRowImplExt: ListBoxRowImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Widget>,
+    <Self as ObjectSubclass>::Type: IsA<ListBoxRow>,
 {
     fn parent_activate(&self) {
         unsafe {
@@ -31,11 +35,19 @@ where
     }
 }
 
-impl<T: ListBoxRowImpl> ListBoxRowImplExt for T where <T as ObjectSubclass>::Type: IsA<glib::Object> {}
+impl<T: ListBoxRowImpl> ListBoxRowImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<ListBoxRow>,
+{
+}
 
 unsafe impl<T: ListBoxRowImpl> IsSubclassable<T> for ListBoxRow
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<ListBoxRow>,
 {
     fn class_init(class: &mut glib::Class<Self>) {
         Self::parent_class_init::<T>(class);
@@ -48,6 +60,8 @@ where
 unsafe extern "C" fn row_activate<T: ListBoxRowImpl>(ptr: *mut ffi::GtkListBoxRow)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<ListBoxRow>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/media_file.rs b/gtk4/src/subclass/media_file.rs
index 845d40153803..8eadc85da467 100644
--- a/gtk4/src/subclass/media_file.rs
+++ b/gtk4/src/subclass/media_file.rs
@@ -5,11 +5,13 @@
 
 use glib::translate::*;
 
-use crate::{ffi, prelude::*, subclass::prelude::*, MediaFile};
+use crate::{ffi, prelude::*, subclass::prelude::*, MediaFile, MediaStream};
 
 pub trait MediaFileImpl: MediaStreamImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<MediaStream>,
+    <Self as ObjectSubclass>::Type: IsA<MediaFile>,
 {
     fn close(&self) {
         self.parent_close()
@@ -22,6 +24,8 @@ where
 pub trait MediaFileImplExt: MediaFileImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<MediaStream>,
+    <Self as ObjectSubclass>::Type: IsA<MediaFile>,
 {
     fn parent_close(&self) {
         unsafe {
@@ -44,11 +48,19 @@ where
     }
 }
 
-impl<T: MediaFileImpl> MediaFileImplExt for T where <T as ObjectSubclass>::Type: IsA<glib::Object> {}
+impl<T: MediaFileImpl> MediaFileImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<MediaStream>,
+    <T as ObjectSubclass>::Type: IsA<MediaFile>,
+{
+}
 
 unsafe impl<T: MediaFileImpl> IsSubclassable<T> for MediaFile
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<MediaStream>,
+    <T as ObjectSubclass>::Type: IsA<MediaFile>,
 {
     fn class_init(class: &mut glib::Class<Self>) {
         Self::parent_class_init::<T>(class);
@@ -62,6 +74,8 @@ where
 unsafe extern "C" fn media_file_close<T: MediaFileImpl>(ptr: *mut ffi::GtkMediaFile)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<MediaStream>,
+    <T as ObjectSubclass>::Type: IsA<MediaFile>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -72,6 +86,8 @@ where
 unsafe extern "C" fn media_file_open<T: MediaFileImpl>(ptr: *mut ffi::GtkMediaFile)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<MediaStream>,
+    <T as ObjectSubclass>::Type: IsA<MediaFile>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/media_stream.rs b/gtk4/src/subclass/media_stream.rs
index 42fefee3f4de..8d07c5cfa3ab 100644
--- a/gtk4/src/subclass/media_stream.rs
+++ b/gtk4/src/subclass/media_stream.rs
@@ -10,6 +10,7 @@ use crate::{ffi, prelude::*, subclass::prelude::*, MediaStream};
 pub trait MediaStreamImpl: ObjectImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<MediaStream>,
 {
     fn pause(&self) {
         self.parent_pause()
@@ -39,6 +40,7 @@ where
 pub trait MediaStreamImplExt: MediaStreamImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<MediaStream>,
 {
     fn parent_pause(&self) {
         unsafe {
@@ -125,14 +127,17 @@ where
     }
 }
 
-impl<T: MediaStreamImpl> MediaStreamImplExt for T where
-    <T as ObjectSubclass>::Type: IsA<glib::Object>
+impl<T: MediaStreamImpl> MediaStreamImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<MediaStream>,
 {
 }
 
 unsafe impl<T: MediaStreamImpl> IsSubclassable<T> for MediaStream
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<MediaStream>,
 {
     fn class_init(class: &mut glib::Class<Self>) {
         Self::parent_class_init::<T>(class);
@@ -152,6 +157,7 @@ where
 unsafe extern "C" fn media_stream_pause<T: MediaStreamImpl>(ptr: *mut ffi::GtkMediaStream)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<MediaStream>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -164,6 +170,7 @@ unsafe extern "C" fn media_stream_play<T: MediaStreamImpl>(
 ) -> glib::ffi::gboolean
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<MediaStream>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -176,6 +183,7 @@ unsafe extern "C" fn media_stream_realize<T: MediaStreamImpl>(
     surface: *mut gdk::ffi::GdkSurface,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<MediaStream>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -188,6 +196,7 @@ unsafe extern "C" fn media_stream_seek<T: MediaStreamImpl>(
     timestamp: i64,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<MediaStream>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -200,6 +209,7 @@ unsafe extern "C" fn media_stream_unrealize<T: MediaStreamImpl>(
     surface: *mut gdk::ffi::GdkSurface,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<MediaStream>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -213,6 +223,7 @@ unsafe extern "C" fn media_stream_update_audio<T: MediaStreamImpl>(
     volume: f64,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<MediaStream>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/native_dialog.rs b/gtk4/src/subclass/native_dialog.rs
index a84f1ecdd67f..990d1120ff2e 100644
--- a/gtk4/src/subclass/native_dialog.rs
+++ b/gtk4/src/subclass/native_dialog.rs
@@ -12,6 +12,7 @@ use crate::{ffi, prelude::*, subclass::prelude::*, NativeDialog, ResponseType};
 pub trait NativeDialogImpl: ObjectImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<NativeDialog>,
 {
     fn response(&self, response: ResponseType) {
         self.parent_response(response)
@@ -31,6 +32,7 @@ where
 pub trait NativeDialogImplExt: NativeDialogImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<NativeDialog>,
 {
     fn parent_response(&self, response: ResponseType) {
         unsafe {
@@ -79,14 +81,17 @@ where
     }
 }
 
-impl<T: NativeDialogImpl> NativeDialogImplExt for T where
-    <T as ObjectSubclass>::Type: IsA<glib::Object>
+impl<T: NativeDialogImpl> NativeDialogImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<NativeDialog>,
 {
 }
 
 unsafe impl<T: NativeDialogImpl> IsSubclassable<T> for NativeDialog
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<NativeDialog>,
 {
     fn class_init(class: &mut glib::Class<Self>) {
         Self::parent_class_init::<T>(class);
@@ -105,6 +110,7 @@ unsafe extern "C" fn dialog_response<T: NativeDialogImpl>(
     responseptr: i32,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<NativeDialog>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -116,6 +122,7 @@ unsafe extern "C" fn dialog_response<T: NativeDialogImpl>(
 unsafe extern "C" fn dialog_show<T: NativeDialogImpl>(ptr: *mut ffi::GtkNativeDialog)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<NativeDialog>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -126,6 +133,7 @@ where
 unsafe extern "C" fn dialog_hide<T: NativeDialogImpl>(ptr: *mut ffi::GtkNativeDialog)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<NativeDialog>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/orientable.rs b/gtk4/src/subclass/orientable.rs
index 87ab8857e1ba..0f0c5cbe7132 100644
--- a/gtk4/src/subclass/orientable.rs
+++ b/gtk4/src/subclass/orientable.rs
@@ -6,13 +6,16 @@
 
 use crate::{prelude::*, subclass::prelude::*, Orientable};
 
-pub trait OrientableImpl: WidgetImpl
+pub trait OrientableImpl: ObjectImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Orientable>,
 {
 }
 
-unsafe impl<T: OrientableImpl> IsImplementable<T> for Orientable where
-    <T as ObjectSubclass>::Type: IsA<glib::Object>
+unsafe impl<T: OrientableImpl> IsImplementable<T> for Orientable
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Orientable>,
 {
 }
diff --git a/gtk4/src/subclass/popover.rs b/gtk4/src/subclass/popover.rs
index db7ce354a27f..37fbe41f6dba 100644
--- a/gtk4/src/subclass/popover.rs
+++ b/gtk4/src/subclass/popover.rs
@@ -5,11 +5,13 @@
 
 use glib::translate::*;
 
-use crate::{ffi, prelude::*, subclass::prelude::*, Popover};
+use crate::{ffi, prelude::*, subclass::prelude::*, Popover, Widget};
 
 pub trait PopoverImpl: WidgetImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Widget>,
+    <Self as ObjectSubclass>::Type: IsA<Popover>,
 {
     fn activate_default(&self) {
         self.parent_activate_default()
@@ -23,6 +25,8 @@ where
 pub trait PopoverImplExt: PopoverImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Widget>,
+    <Self as ObjectSubclass>::Type: IsA<Popover>,
 {
     fn parent_activate_default(&self) {
         unsafe {
@@ -45,11 +49,19 @@ where
     }
 }
 
-impl<T: PopoverImpl> PopoverImplExt for T where <T as ObjectSubclass>::Type: IsA<glib::Object> {}
+impl<T: PopoverImpl> PopoverImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Popover>,
+{
+}
 
 unsafe impl<T: PopoverImpl> IsSubclassable<T> for Popover
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Popover>,
 {
     fn class_init(class: &mut glib::Class<Self>) {
         Self::parent_class_init::<T>(class);
@@ -63,6 +75,8 @@ where
 unsafe extern "C" fn popover_activate_default<T: PopoverImpl>(ptr: *mut ffi::GtkPopover)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Popover>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -73,6 +87,8 @@ where
 unsafe extern "C" fn popover_closed<T: PopoverImpl>(ptr: *mut ffi::GtkPopover)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Popover>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/print_operation.rs b/gtk4/src/subclass/print_operation.rs
index de2c76ee335b..62328137de83 100644
--- a/gtk4/src/subclass/print_operation.rs
+++ b/gtk4/src/subclass/print_operation.rs
@@ -13,6 +13,8 @@ use crate::{
 pub trait PrintOperationImpl: PrintOperationPreviewImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<PrintOperationPreview>,
+    <Self as ObjectSubclass>::Type: IsA<PrintOperation>,
 {
     fn begin_print(&self, context: &PrintContext) {
         self.parent_begin_print(context)
@@ -67,6 +69,8 @@ where
 pub trait PrintOperationImplExt: PrintOperationImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<PrintOperationPreview>,
+    <Self as ObjectSubclass>::Type: IsA<PrintOperation>,
 {
     fn parent_begin_print(&self, context: &PrintContext) {
         unsafe {
@@ -269,14 +273,19 @@ where
     }
 }
 
-impl<T: PrintOperationImpl> PrintOperationImplExt for T where
-    <T as ObjectSubclass>::Type: IsA<glib::Object>
+impl<T: PrintOperationImpl> PrintOperationImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<PrintOperationPreview>,
+    <T as ObjectSubclass>::Type: IsA<PrintOperation>,
 {
 }
 
 unsafe impl<T: PrintOperationImpl> IsSubclassable<T> for PrintOperation
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<PrintOperationPreview>,
+    <T as ObjectSubclass>::Type: IsA<PrintOperation>,
 {
     fn class_init(class: &mut glib::Class<Self>) {
         Self::parent_class_init::<T>(class);
@@ -299,6 +308,8 @@ unsafe extern "C" fn print_operation_begin_print<T: PrintOperationImpl>(
     contextptr: *mut ffi::GtkPrintContext,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<PrintOperationPreview>,
+    <T as ObjectSubclass>::Type: IsA<PrintOperation>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -312,6 +323,8 @@ unsafe extern "C" fn print_operation_create_custom_widget<T: PrintOperationImpl>
 ) -> *mut ffi::GtkWidget
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<PrintOperationPreview>,
+    <T as ObjectSubclass>::Type: IsA<PrintOperation>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -324,6 +337,8 @@ unsafe extern "C" fn print_operation_custom_widget_apply<T: PrintOperationImpl>(
     widgetptr: *mut ffi::GtkWidget,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<PrintOperationPreview>,
+    <T as ObjectSubclass>::Type: IsA<PrintOperation>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -337,6 +352,8 @@ unsafe extern "C" fn print_operation_done<T: PrintOperationImpl>(
     resultptr: ffi::GtkPrintOperationResult,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<PrintOperationPreview>,
+    <T as ObjectSubclass>::Type: IsA<PrintOperation>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -350,6 +367,8 @@ unsafe extern "C" fn print_operation_draw_page<T: PrintOperationImpl>(
     page_nr: i32,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<PrintOperationPreview>,
+    <T as ObjectSubclass>::Type: IsA<PrintOperation>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -363,6 +382,8 @@ unsafe extern "C" fn print_operation_end_print<T: PrintOperationImpl>(
     contextptr: *mut ffi::GtkPrintContext,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<PrintOperationPreview>,
+    <T as ObjectSubclass>::Type: IsA<PrintOperation>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -378,6 +399,8 @@ unsafe extern "C" fn print_operation_request_page_setup<T: PrintOperationImpl>(
     setupptr: *mut ffi::GtkPageSetup,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<PrintOperationPreview>,
+    <T as ObjectSubclass>::Type: IsA<PrintOperation>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -391,6 +414,8 @@ unsafe extern "C" fn print_operation_status_changed<T: PrintOperationImpl>(
     ptr: *mut ffi::GtkPrintOperation,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<PrintOperationPreview>,
+    <T as ObjectSubclass>::Type: IsA<PrintOperation>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -405,6 +430,8 @@ unsafe extern "C" fn print_operation_update_custom_widget<T: PrintOperationImpl>
     settingsptr: *mut ffi::GtkPrintSettings,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<PrintOperationPreview>,
+    <T as ObjectSubclass>::Type: IsA<PrintOperation>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/print_operation_preview.rs b/gtk4/src/subclass/print_operation_preview.rs
index a6e854a5848a..ed28af5ab550 100644
--- a/gtk4/src/subclass/print_operation_preview.rs
+++ b/gtk4/src/subclass/print_operation_preview.rs
@@ -13,6 +13,7 @@ use crate::{
 pub trait PrintOperationPreviewImpl: ObjectImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<PrintOperationPreview>,
 {
     fn ready(&self, context: &PrintContext) {
         self.parent_ready(context)
@@ -30,6 +31,7 @@ where
 pub trait PrintOperationPreviewImplExt: PrintOperationPreviewImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<PrintOperationPreview>,
 {
     fn parent_ready(&self, context: &PrintContext) {
         unsafe {
@@ -133,14 +135,17 @@ where
     }
 }
 
-impl<T: PrintOperationPreviewImpl> PrintOperationPreviewImplExt for T where
-    <T as ObjectSubclass>::Type: IsA<glib::Object>
+impl<T: PrintOperationPreviewImpl> PrintOperationPreviewImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<PrintOperationPreview>,
 {
 }
 
 unsafe impl<T: PrintOperationPreviewImpl> IsImplementable<T> for PrintOperationPreview
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<PrintOperationPreview>,
 {
     fn interface_init(iface: &mut glib::Interface<Self>) {
         let iface = iface.as_mut();
@@ -160,6 +165,7 @@ unsafe extern "C" fn print_operation_preview_ready<T: PrintOperationPreviewImpl>
     contextptr: *mut ffi::GtkPrintContext,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<PrintOperationPreview>,
 {
     let instance = &*(print_operation_preview as *mut T::Instance);
     let imp = instance.imp();
@@ -174,6 +180,7 @@ unsafe extern "C" fn print_operation_preview_got_page_size<T: PrintOperationPrev
     setupptr: *mut ffi::GtkPageSetup,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<PrintOperationPreview>,
 {
     let instance = &*(print_operation_preview as *mut T::Instance);
     let imp = instance.imp();
@@ -189,6 +196,7 @@ unsafe extern "C" fn print_operation_preview_render_page<T: PrintOperationPrevie
     page_nr: i32,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<PrintOperationPreview>,
 {
     let instance = &*(print_operation_preview as *mut T::Instance);
     let imp = instance.imp();
@@ -202,6 +210,7 @@ unsafe extern "C" fn print_operation_preview_is_selected<T: PrintOperationPrevie
 ) -> glib::ffi::gboolean
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<PrintOperationPreview>,
 {
     let instance = &*(print_operation_preview as *mut T::Instance);
     let imp = instance.imp();
@@ -213,6 +222,7 @@ unsafe extern "C" fn print_operation_preview_end_preview<T: PrintOperationPrevie
     print_operation_preview: *mut ffi::GtkPrintOperationPreview,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<PrintOperationPreview>,
 {
     let instance = &*(print_operation_preview as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/range.rs b/gtk4/src/subclass/range.rs
index 05a4c2cb10fc..1516a2cba332 100644
--- a/gtk4/src/subclass/range.rs
+++ b/gtk4/src/subclass/range.rs
@@ -5,11 +5,13 @@
 
 use glib::translate::*;
 
-use crate::{ffi, prelude::*, subclass::prelude::*, Border, Range, ScrollType};
+use crate::{ffi, prelude::*, subclass::prelude::*, Border, Range, ScrollType, Widget};
 
 pub trait RangeImpl: WidgetImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Widget>,
+    <Self as ObjectSubclass>::Type: IsA<Range>,
 {
     fn adjust_bounds(&self, new_value: f64) {
         self.parent_adjust_bounds(new_value)
@@ -36,6 +38,8 @@ where
 pub trait RangeImplExt: RangeImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Widget>,
+    <Self as ObjectSubclass>::Type: IsA<Range>,
 {
     fn parent_adjust_bounds(&self, new_value: f64) {
         unsafe {
@@ -104,11 +108,19 @@ where
     }
 }
 
-impl<T: RangeImpl> RangeImplExt for T where <T as ObjectSubclass>::Type: IsA<glib::Object> {}
+impl<T: RangeImpl> RangeImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Range>,
+{
+}
 
 unsafe impl<T: RangeImpl> IsSubclassable<T> for Range
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Range>,
 {
     fn class_init(class: &mut glib::Class<Self>) {
         Self::parent_class_init::<T>(class);
@@ -125,6 +137,8 @@ where
 unsafe extern "C" fn range_adjust_bounds<T: RangeImpl>(ptr: *mut ffi::GtkRange, new_value: f64)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Range>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -139,6 +153,8 @@ unsafe extern "C" fn range_change_value<T: RangeImpl>(
 ) -> glib::ffi::gboolean
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Range>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -152,6 +168,8 @@ unsafe extern "C" fn range_get_range_border<T: RangeImpl>(
     borderptr: *mut ffi::GtkBorder,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Range>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -165,6 +183,8 @@ unsafe extern "C" fn range_move_slider<T: RangeImpl>(
     scroll_type: ffi::GtkScrollType,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Range>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -175,6 +195,8 @@ unsafe extern "C" fn range_move_slider<T: RangeImpl>(
 unsafe extern "C" fn range_value_changed<T: RangeImpl>(ptr: *mut ffi::GtkRange)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Range>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/recent_manager.rs b/gtk4/src/subclass/recent_manager.rs
index 2c5fc9f1bb0b..d44adad32210 100644
--- a/gtk4/src/subclass/recent_manager.rs
+++ b/gtk4/src/subclass/recent_manager.rs
@@ -10,6 +10,7 @@ use crate::{ffi, prelude::*, subclass::prelude::*, RecentManager};
 pub trait RecentManagerImpl: ObjectImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<RecentManager>,
 {
     fn changed(&self) {
         self.parent_changed()
@@ -19,6 +20,7 @@ where
 pub trait RecentManagerImplExt: RecentManagerImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<RecentManager>,
 {
     fn parent_changed(&self) {
         unsafe {
@@ -35,14 +37,17 @@ where
     }
 }
 
-impl<T: RecentManagerImpl> RecentManagerImplExt for T where
-    <T as ObjectSubclass>::Type: IsA<glib::Object>
+impl<T: RecentManagerImpl> RecentManagerImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<RecentManager>,
 {
 }
 
 unsafe impl<T: RecentManagerImpl> IsSubclassable<T> for RecentManager
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<RecentManager>,
 {
     fn class_init(class: &mut glib::Class<Self>) {
         Self::parent_class_init::<T>(class);
@@ -57,6 +62,7 @@ where
 unsafe extern "C" fn recent_manager_changed<T: RecentManagerImpl>(ptr: *mut ffi::GtkRecentManager)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<RecentManager>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/scale.rs b/gtk4/src/subclass/scale.rs
index f64b429714b9..0a48637483e4 100644
--- a/gtk4/src/subclass/scale.rs
+++ b/gtk4/src/subclass/scale.rs
@@ -5,11 +5,14 @@
 
 use glib::translate::*;
 
-use crate::{ffi, prelude::*, subclass::prelude::*, Scale};
+use crate::{ffi, prelude::*, subclass::prelude::*, Range, Scale, Widget};
 
 pub trait ScaleImpl: RangeImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Widget>,
+    <Self as ObjectSubclass>::Type: IsA<Range>,
+    <Self as ObjectSubclass>::Type: IsA<Scale>,
 {
     #[doc(alias = "get_layout_offsets")]
     fn layout_offsets(&self) -> (i32, i32) {
@@ -20,6 +23,9 @@ where
 pub trait ScaleImplExt: ScaleImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Widget>,
+    <Self as ObjectSubclass>::Type: IsA<Range>,
+    <Self as ObjectSubclass>::Type: IsA<Scale>,
 {
     fn parent_layout_offsets(&self) -> (i32, i32) {
         unsafe {
@@ -39,11 +45,21 @@ where
     }
 }
 
-impl<T: ScaleImpl> ScaleImplExt for T where <T as ObjectSubclass>::Type: IsA<glib::Object> {}
+impl<T: ScaleImpl> ScaleImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Range>,
+    <T as ObjectSubclass>::Type: IsA<Scale>,
+{
+}
 
 unsafe impl<T: ScaleImpl> IsSubclassable<T> for Scale
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Range>,
+    <T as ObjectSubclass>::Type: IsA<Scale>,
 {
     fn class_init(class: &mut glib::Class<Self>) {
         Self::parent_class_init::<T>(class);
@@ -59,6 +75,9 @@ unsafe extern "C" fn scale_get_layout_offsets<T: ScaleImpl>(
     y_ptr: *mut libc::c_int,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Range>,
+    <T as ObjectSubclass>::Type: IsA<Scale>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/scale_button.rs b/gtk4/src/subclass/scale_button.rs
index 548d52de754c..967e8116fcd8 100644
--- a/gtk4/src/subclass/scale_button.rs
+++ b/gtk4/src/subclass/scale_button.rs
@@ -5,11 +5,13 @@
 
 use glib::translate::*;
 
-use crate::{ffi, prelude::*, subclass::prelude::*, ScaleButton};
+use crate::{ffi, prelude::*, subclass::prelude::*, ScaleButton, Widget};
 
 pub trait ScaleButtonImpl: WidgetImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Widget>,
+    <Self as ObjectSubclass>::Type: IsA<ScaleButton>,
 {
     fn value_changed(&self, new_value: f64) {
         self.parent_value_changed(new_value)
@@ -19,6 +21,8 @@ where
 pub trait ScaleButtonImplExt: ScaleButtonImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Widget>,
+    <Self as ObjectSubclass>::Type: IsA<ScaleButton>,
 {
     fn parent_value_changed(&self, new_value: f64) {
         unsafe {
@@ -34,14 +38,19 @@ where
     }
 }
 
-impl<T: ScaleButtonImpl> ScaleButtonImplExt for T where
-    <T as ObjectSubclass>::Type: IsA<glib::Object>
+impl<T: ScaleButtonImpl> ScaleButtonImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<ScaleButton>,
 {
 }
 
 unsafe impl<T: ScaleButtonImpl> IsSubclassable<T> for ScaleButton
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<ScaleButton>,
 {
     fn class_init(class: &mut glib::Class<Self>) {
         Self::parent_class_init::<T>(class);
@@ -56,6 +65,8 @@ unsafe extern "C" fn scale_button_value_changed<T: ScaleButtonImpl>(
     new_value: f64,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<ScaleButton>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/scrollable.rs b/gtk4/src/subclass/scrollable.rs
index 0ea2a0407780..337160101b1a 100644
--- a/gtk4/src/subclass/scrollable.rs
+++ b/gtk4/src/subclass/scrollable.rs
@@ -6,11 +6,13 @@
 
 use glib::translate::*;
 
-use crate::{ffi, prelude::*, subclass::prelude::*, Border, Scrollable};
+use crate::{ffi, prelude::*, subclass::prelude::*, Border, Scrollable, Widget};
 
 pub trait ScrollableImpl: WidgetImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Widget>,
+    <Self as ObjectSubclass>::Type: IsA<Scrollable>,
 {
     #[doc(alias = "get_border")]
     fn border(&self) -> Option<Border> {
@@ -21,6 +23,8 @@ where
 pub trait ScrollableImplExt: ScrollableImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Widget>,
+    <Self as ObjectSubclass>::Type: IsA<Scrollable>,
 {
     fn parent_border(&self) -> Option<Border> {
         unsafe {
@@ -42,11 +46,19 @@ where
     }
 }
 
-impl<T: ScrollableImpl> ScrollableImplExt for T where <T as ObjectSubclass>::Type: IsA<glib::Object> {}
+impl<T: ScrollableImpl> ScrollableImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Scrollable>,
+{
+}
 
 unsafe impl<T: ScrollableImpl> IsImplementable<T> for Scrollable
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Scrollable>,
 {
     fn interface_init(iface: &mut glib::Interface<Self>) {
         let iface = iface.as_mut();
@@ -61,6 +73,8 @@ unsafe extern "C" fn scrollable_get_border<T: ScrollableImpl>(
 ) -> glib::ffi::gboolean
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Scrollable>,
 {
     let instance = &*(scrollable as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/section_model.rs b/gtk4/src/subclass/section_model.rs
index 46869d6ae838..88c7029d10a0 100644
--- a/gtk4/src/subclass/section_model.rs
+++ b/gtk4/src/subclass/section_model.rs
@@ -12,6 +12,7 @@ pub trait SectionModelImpl: ListModelImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
     <Self as ObjectSubclass>::Type: IsA<gio::ListModel>,
+    <Self as ObjectSubclass>::Type: IsA<SectionModel>,
 {
     #[doc(alias = "get_section")]
     fn section(&self, position: u32) -> (u32, u32) {
@@ -23,6 +24,7 @@ pub trait SectionModelImplExt: SectionModelImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
     <Self as ObjectSubclass>::Type: IsA<gio::ListModel>,
+    <Self as ObjectSubclass>::Type: IsA<SectionModel>,
 {
     fn parent_section(&self, position: u32) -> (u32, u32) {
         unsafe {
@@ -54,6 +56,7 @@ impl<T: SectionModelImpl> SectionModelImplExt for T
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
     <T as ObjectSubclass>::Type: IsA<gio::ListModel>,
+    <T as ObjectSubclass>::Type: IsA<SectionModel>,
 {
 }
 
@@ -61,6 +64,7 @@ unsafe impl<T: SectionModelImpl> IsImplementable<T> for SectionModel
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
     <T as ObjectSubclass>::Type: IsA<gio::ListModel>,
+    <T as ObjectSubclass>::Type: IsA<SectionModel>,
 {
     fn interface_init(iface: &mut glib::Interface<Self>) {
         let iface = iface.as_mut();
@@ -79,6 +83,7 @@ unsafe extern "C" fn model_get_section<T: SectionModelImpl>(
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
     <T as ObjectSubclass>::Type: IsA<gio::ListModel>,
+    <T as ObjectSubclass>::Type: IsA<SectionModel>,
 {
     let instance = &*(model as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/selection_model.rs b/gtk4/src/subclass/selection_model.rs
index 10a2f466ac70..b4aa31ba87f0 100644
--- a/gtk4/src/subclass/selection_model.rs
+++ b/gtk4/src/subclass/selection_model.rs
@@ -12,6 +12,7 @@ pub trait SelectionModelImpl: ListModelImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
     <Self as ObjectSubclass>::Type: IsA<gio::ListModel>,
+    <Self as ObjectSubclass>::Type: IsA<SelectionModel>,
 {
     #[doc(alias = "get_selection_in_range")]
     fn selection_in_range(&self, position: u32, n_items: u32) -> Bitset {
@@ -55,6 +56,7 @@ pub trait SelectionModelImplExt: SelectionModelImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
     <Self as ObjectSubclass>::Type: IsA<gio::ListModel>,
+    <Self as ObjectSubclass>::Type: IsA<SelectionModel>,
 {
     fn parent_selection_in_range(&self, position: u32, n_items: u32) -> Bitset {
         unsafe {
@@ -245,6 +247,7 @@ impl<T: SelectionModelImpl> SelectionModelImplExt for T
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
     <T as ObjectSubclass>::Type: IsA<gio::ListModel>,
+    <T as ObjectSubclass>::Type: IsA<SelectionModel>,
 {
 }
 
@@ -252,6 +255,7 @@ unsafe impl<T: SelectionModelImpl> IsImplementable<T> for SelectionModel
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
     <T as ObjectSubclass>::Type: IsA<gio::ListModel>,
+    <T as ObjectSubclass>::Type: IsA<SelectionModel>,
 {
     fn interface_init(iface: &mut glib::Interface<Self>) {
         let iface = iface.as_mut();
@@ -278,6 +282,7 @@ unsafe extern "C" fn model_get_selection_in_range<T: SelectionModelImpl>(
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
     <T as ObjectSubclass>::Type: IsA<gio::ListModel>,
+    <T as ObjectSubclass>::Type: IsA<SelectionModel>,
 {
     let instance = &*(model as *mut T::Instance);
     let imp = instance.imp();
@@ -292,6 +297,7 @@ unsafe extern "C" fn model_is_selected<T: SelectionModelImpl>(
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
     <T as ObjectSubclass>::Type: IsA<gio::ListModel>,
+    <T as ObjectSubclass>::Type: IsA<SelectionModel>,
 {
     let instance = &*(model as *mut T::Instance);
     let imp = instance.imp();
@@ -305,6 +311,7 @@ unsafe extern "C" fn model_select_all<T: SelectionModelImpl>(
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
     <T as ObjectSubclass>::Type: IsA<gio::ListModel>,
+    <T as ObjectSubclass>::Type: IsA<SelectionModel>,
 {
     let instance = &*(model as *mut T::Instance);
     let imp = instance.imp();
@@ -320,6 +327,7 @@ unsafe extern "C" fn model_select_item<T: SelectionModelImpl>(
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
     <T as ObjectSubclass>::Type: IsA<gio::ListModel>,
+    <T as ObjectSubclass>::Type: IsA<SelectionModel>,
 {
     let instance = &*(model as *mut T::Instance);
     let imp = instance.imp();
@@ -337,6 +345,7 @@ unsafe extern "C" fn model_select_range<T: SelectionModelImpl>(
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
     <T as ObjectSubclass>::Type: IsA<gio::ListModel>,
+    <T as ObjectSubclass>::Type: IsA<SelectionModel>,
 {
     let instance = &*(model as *mut T::Instance);
     let imp = instance.imp();
@@ -353,6 +362,7 @@ unsafe extern "C" fn model_set_selection<T: SelectionModelImpl>(
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
     <T as ObjectSubclass>::Type: IsA<gio::ListModel>,
+    <T as ObjectSubclass>::Type: IsA<SelectionModel>,
 {
     let instance = &*(model as *mut T::Instance);
     let imp = instance.imp();
@@ -369,6 +379,7 @@ unsafe extern "C" fn model_unselect_all<T: SelectionModelImpl>(
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
     <T as ObjectSubclass>::Type: IsA<gio::ListModel>,
+    <T as ObjectSubclass>::Type: IsA<SelectionModel>,
 {
     let instance = &*(model as *mut T::Instance);
     let imp = instance.imp();
@@ -383,6 +394,7 @@ unsafe extern "C" fn model_unselect_item<T: SelectionModelImpl>(
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
     <T as ObjectSubclass>::Type: IsA<gio::ListModel>,
+    <T as ObjectSubclass>::Type: IsA<SelectionModel>,
 {
     let instance = &*(model as *mut T::Instance);
     let imp = instance.imp();
@@ -398,6 +410,7 @@ unsafe extern "C" fn model_unselect_range<T: SelectionModelImpl>(
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
     <T as ObjectSubclass>::Type: IsA<gio::ListModel>,
+    <T as ObjectSubclass>::Type: IsA<SelectionModel>,
 {
     let instance = &*(model as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/shortcut_manager.rs b/gtk4/src/subclass/shortcut_manager.rs
index 9c1f90185695..f78fdf978fee 100644
--- a/gtk4/src/subclass/shortcut_manager.rs
+++ b/gtk4/src/subclass/shortcut_manager.rs
@@ -11,6 +11,7 @@ use crate::{ffi, prelude::*, subclass::prelude::*, ShortcutController, ShortcutM
 pub trait ShortcutManagerImpl: ObjectImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<ShortcutManager>,
 {
     fn add_controller(&self, controller: &ShortcutController) {
         self.parent_add_controller(controller);
@@ -24,6 +25,7 @@ where
 pub trait ShortcutManagerImplExt: ShortcutManagerImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<ShortcutManager>,
 {
     fn parent_add_controller(&self, controller: &ShortcutController) {
         unsafe {
@@ -66,14 +68,17 @@ where
     }
 }
 
-impl<T: ShortcutManagerImpl> ShortcutManagerImplExt for T where
-    <T as ObjectSubclass>::Type: IsA<glib::Object>
+impl<T: ShortcutManagerImpl> ShortcutManagerImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<ShortcutManager>,
 {
 }
 
 unsafe impl<T: ShortcutManagerImpl> IsImplementable<T> for ShortcutManager
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<ShortcutManager>,
 {
     fn interface_init(iface: &mut glib::Interface<Self>) {
         let iface = iface.as_mut();
@@ -90,6 +95,7 @@ unsafe extern "C" fn shortcut_manager_add_controller<T: ShortcutManagerImpl>(
     controller: *mut ffi::GtkShortcutController,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<ShortcutManager>,
 {
     let instance = &*(shortcut_manager as *mut T::Instance);
     let imp = instance.imp();
@@ -102,6 +108,7 @@ unsafe extern "C" fn shortcut_manager_remove_controller<T: ShortcutManagerImpl>(
     controller: *mut ffi::GtkShortcutController,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<ShortcutManager>,
 {
     let instance = &*(shortcut_manager as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/sorter.rs b/gtk4/src/subclass/sorter.rs
index 639f143b1458..29ff24b767f0 100644
--- a/gtk4/src/subclass/sorter.rs
+++ b/gtk4/src/subclass/sorter.rs
@@ -10,6 +10,7 @@ use crate::{ffi, prelude::*, subclass::prelude::*, Ordering, Sorter, SorterOrder
 pub trait SorterImpl: ObjectImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Sorter>,
 {
     fn compare(&self, item1: &Object, item2: &Object) -> Ordering {
         self.parent_compare(item1, item2)
@@ -23,6 +24,7 @@ where
 pub trait SorterImplExt: SorterImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Sorter>,
 {
     fn parent_compare(&self, item1: &Object, item2: &Object) -> Ordering {
         unsafe {
@@ -51,11 +53,17 @@ where
     }
 }
 
-impl<T: SorterImpl> SorterImplExt for T where <T as ObjectSubclass>::Type: IsA<glib::Object> {}
+impl<T: SorterImpl> SorterImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Sorter>,
+{
+}
 
 unsafe impl<T: SorterImpl> IsSubclassable<T> for Sorter
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Sorter>,
 {
     fn class_init(class: &mut glib::Class<Self>) {
         Self::parent_class_init::<T>(class);
@@ -75,6 +83,7 @@ unsafe extern "C" fn sorter_compare<T: SorterImpl>(
 ) -> ffi::GtkOrdering
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Sorter>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -88,6 +97,7 @@ unsafe extern "C" fn sorter_get_order<T: SorterImpl>(
 ) -> ffi::GtkSorterOrder
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Sorter>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/style_context.rs b/gtk4/src/subclass/style_context.rs
index bd1d909afd5e..c10c3be2c326 100644
--- a/gtk4/src/subclass/style_context.rs
+++ b/gtk4/src/subclass/style_context.rs
@@ -12,6 +12,7 @@ use crate::{ffi, prelude::*, subclass::prelude::*, StyleContext};
 pub trait StyleContextImpl: ObjectImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<StyleContext>,
 {
     fn changed(&self) {
         self.parent_changed()
@@ -23,6 +24,7 @@ where
 pub trait StyleContextImplExt: StyleContextImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<StyleContext>,
 {
     fn parent_changed(&self) {
         unsafe {
@@ -39,14 +41,17 @@ where
     }
 }
 
-impl<T: StyleContextImpl> StyleContextImplExt for T where
-    <T as ObjectSubclass>::Type: IsA<glib::Object>
+impl<T: StyleContextImpl> StyleContextImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<StyleContext>,
 {
 }
 
 unsafe impl<T: StyleContextImpl> IsSubclassable<T> for StyleContext
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<StyleContext>,
 {
     fn class_init(class: &mut glib::Class<Self>) {
         Self::parent_class_init::<T>(class);
@@ -60,6 +65,7 @@ where
 unsafe extern "C" fn style_context_changed<T: StyleContextImpl>(ptr: *mut ffi::GtkStyleContext)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<StyleContext>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/symbolic_paintable.rs b/gtk4/src/subclass/symbolic_paintable.rs
index 3a2e45f782a3..8c88469007fd 100644
--- a/gtk4/src/subclass/symbolic_paintable.rs
+++ b/gtk4/src/subclass/symbolic_paintable.rs
@@ -11,6 +11,8 @@ use crate::{ffi, prelude::*, subclass::prelude::*, SymbolicPaintable};
 pub trait SymbolicPaintableImpl: PaintableImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<gdk::Paintable>,
+    <Self as ObjectSubclass>::Type: IsA<SymbolicPaintable>,
 {
     fn snapshot_symbolic(
         &self,
@@ -26,6 +28,8 @@ where
 pub trait SymbolicPaintableImplExt: SymbolicPaintableImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<gdk::Paintable>,
+    <Self as ObjectSubclass>::Type: IsA<SymbolicPaintable>,
 {
     fn parent_snapshot_symbolic(
         &self,
@@ -55,14 +59,19 @@ where
     }
 }
 
-impl<T: SymbolicPaintableImpl> SymbolicPaintableImplExt for T where
-    <T as ObjectSubclass>::Type: IsA<glib::Object>
+impl<T: SymbolicPaintableImpl> SymbolicPaintableImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<gdk::Paintable>,
+    <T as ObjectSubclass>::Type: IsA<SymbolicPaintable>,
 {
 }
 
 unsafe impl<T: SymbolicPaintableImpl> IsImplementable<T> for SymbolicPaintable
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<gdk::Paintable>,
+    <T as ObjectSubclass>::Type: IsA<SymbolicPaintable>,
 {
     fn interface_init(iface: &mut glib::Interface<Self>) {
         let iface = iface.as_mut();
@@ -82,6 +91,8 @@ unsafe extern "C" fn symbolic_paintable_snapshot_symbolic<T: SymbolicPaintableIm
     n_colors: usize,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<gdk::Paintable>,
+    <T as ObjectSubclass>::Type: IsA<SymbolicPaintable>,
 {
     let instance = &*(paintable as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/text_buffer.rs b/gtk4/src/subclass/text_buffer.rs
index 24c946b13a6f..c9f92f368af8 100644
--- a/gtk4/src/subclass/text_buffer.rs
+++ b/gtk4/src/subclass/text_buffer.rs
@@ -12,6 +12,7 @@ use crate::{
 pub trait TextBufferImpl: ObjectImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<TextBuffer>,
 {
     fn apply_tag(&self, tag: &TextTag, start: &TextIter, end: &TextIter) {
         self.parent_apply_tag(tag, start, end)
@@ -63,6 +64,7 @@ where
 pub trait TextBufferImplExt: TextBufferImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<TextBuffer>,
 {
     fn parent_apply_tag(&self, tag: &TextTag, start: &TextIter, end: &TextIter) {
         unsafe {
@@ -252,11 +254,17 @@ where
     }
 }
 
-impl<T: TextBufferImpl> TextBufferImplExt for T where <T as ObjectSubclass>::Type: IsA<glib::Object> {}
+impl<T: TextBufferImpl> TextBufferImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<TextBuffer>,
+{
+}
 
 unsafe impl<T: TextBufferImpl> IsSubclassable<T> for TextBuffer
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<TextBuffer>,
 {
     fn class_init(class: &mut glib::Class<Self>) {
         Self::parent_class_init::<T>(class);
@@ -289,6 +297,7 @@ unsafe extern "C" fn text_buffer_apply_tag<T: TextBufferImpl>(
     end_ptr: *const ffi::GtkTextIter,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<TextBuffer>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -303,6 +312,7 @@ unsafe extern "C" fn text_buffer_apply_tag<T: TextBufferImpl>(
 unsafe extern "C" fn text_buffer_begin_user_action<T: TextBufferImpl>(ptr: *mut ffi::GtkTextBuffer)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<TextBuffer>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -313,6 +323,7 @@ where
 unsafe extern "C" fn text_buffer_changed<T: TextBufferImpl>(ptr: *mut ffi::GtkTextBuffer)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<TextBuffer>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -326,6 +337,7 @@ unsafe extern "C" fn text_buffer_delete_range<T: TextBufferImpl>(
     end_ptr: *mut ffi::GtkTextIter,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<TextBuffer>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -342,6 +354,7 @@ unsafe extern "C" fn text_buffer_delete_range<T: TextBufferImpl>(
 unsafe extern "C" fn text_buffer_end_user_action<T: TextBufferImpl>(ptr: *mut ffi::GtkTextBuffer)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<TextBuffer>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -355,6 +368,7 @@ unsafe extern "C" fn text_buffer_insert_child_anchor<T: TextBufferImpl>(
     anchor_ptr: *mut ffi::GtkTextChildAnchor,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<TextBuffer>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -371,6 +385,7 @@ unsafe extern "C" fn text_buffer_insert_paintable<T: TextBufferImpl>(
     paintable_ptr: *mut gdk::ffi::GdkPaintable,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<TextBuffer>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -388,6 +403,7 @@ unsafe extern "C" fn text_buffer_insert_text<T: TextBufferImpl>(
     _length: libc::c_int,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<TextBuffer>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -402,6 +418,7 @@ unsafe extern "C" fn text_buffer_insert_text<T: TextBufferImpl>(
 unsafe extern "C" fn text_buffer_modified_changed<T: TextBufferImpl>(ptr: *mut ffi::GtkTextBuffer)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<TextBuffer>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -414,6 +431,7 @@ unsafe extern "C" fn text_buffer_mark_deleted<T: TextBufferImpl>(
     mark: *mut ffi::GtkTextMark,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<TextBuffer>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -427,6 +445,7 @@ unsafe extern "C" fn text_buffer_mark_set<T: TextBufferImpl>(
     mark: *mut ffi::GtkTextMark,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<TextBuffer>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -439,6 +458,7 @@ unsafe extern "C" fn text_buffer_paste_done<T: TextBufferImpl>(
     clipboard_ptr: *mut gdk::ffi::GdkClipboard,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<TextBuffer>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -449,6 +469,7 @@ unsafe extern "C" fn text_buffer_paste_done<T: TextBufferImpl>(
 unsafe extern "C" fn text_buffer_redo<T: TextBufferImpl>(ptr: *mut ffi::GtkTextBuffer)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<TextBuffer>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -463,6 +484,7 @@ unsafe extern "C" fn text_buffer_remove_tag<T: TextBufferImpl>(
     end: *const ffi::GtkTextIter,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<TextBuffer>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -477,6 +499,7 @@ unsafe extern "C" fn text_buffer_remove_tag<T: TextBufferImpl>(
 unsafe extern "C" fn text_buffer_undo<T: TextBufferImpl>(ptr: *mut ffi::GtkTextBuffer)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<TextBuffer>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/text_view.rs b/gtk4/src/subclass/text_view.rs
index 22d6334deac3..42c14988164e 100644
--- a/gtk4/src/subclass/text_view.rs
+++ b/gtk4/src/subclass/text_view.rs
@@ -7,12 +7,14 @@ use glib::translate::*;
 
 use crate::{
     ffi, prelude::*, subclass::prelude::*, DeleteType, MovementStep, Snapshot, TextExtendSelection,
-    TextIter, TextView, TextViewLayer,
+    TextIter, TextView, TextViewLayer, Widget,
 };
 
 pub trait TextViewImpl: WidgetImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Widget>,
+    <Self as ObjectSubclass>::Type: IsA<TextView>,
 {
     fn backspace(&self) {
         self.parent_backspace()
@@ -72,6 +74,8 @@ where
 pub trait TextViewImplExt: TextViewImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Widget>,
+    <Self as ObjectSubclass>::Type: IsA<TextView>,
 {
     fn parent_backspace(&self) {
         unsafe {
@@ -224,11 +228,19 @@ where
     }
 }
 
-impl<T: TextViewImpl> TextViewImplExt for T where <T as ObjectSubclass>::Type: IsA<glib::Object> {}
+impl<T: TextViewImpl> TextViewImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<TextView>,
+{
+}
 
 unsafe impl<T: TextViewImpl> IsSubclassable<T> for TextView
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<TextView>,
 {
     fn class_init(class: &mut glib::Class<Self>) {
         Self::parent_class_init::<T>(class);
@@ -252,6 +264,8 @@ where
 unsafe extern "C" fn text_view_backspace<T: TextViewImpl>(ptr: *mut ffi::GtkTextView)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<TextView>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -262,6 +276,8 @@ where
 unsafe extern "C" fn text_view_copy_clipboard<T: TextViewImpl>(ptr: *mut ffi::GtkTextView)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<TextView>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -272,6 +288,8 @@ where
 unsafe extern "C" fn text_view_cut_clipboard<T: TextViewImpl>(ptr: *mut ffi::GtkTextView)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<TextView>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -285,6 +303,8 @@ unsafe extern "C" fn text_view_delete_from_cursor<T: TextViewImpl>(
     count: i32,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<TextView>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -301,6 +321,8 @@ unsafe extern "C" fn text_view_extend_selection<T: TextViewImpl>(
 ) -> glib::ffi::gboolean
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<TextView>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -325,6 +347,8 @@ unsafe extern "C" fn text_view_insert_at_cursor<T: TextViewImpl>(
     text_ptr: *const libc::c_char,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<TextView>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -336,6 +360,8 @@ unsafe extern "C" fn text_view_insert_at_cursor<T: TextViewImpl>(
 unsafe extern "C" fn text_view_insert_emoji<T: TextViewImpl>(ptr: *mut ffi::GtkTextView)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<TextView>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -350,6 +376,8 @@ unsafe extern "C" fn text_view_move_cursor<T: TextViewImpl>(
     extend_selection: glib::ffi::gboolean,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<TextView>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -360,6 +388,8 @@ unsafe extern "C" fn text_view_move_cursor<T: TextViewImpl>(
 unsafe extern "C" fn text_view_paste_clipboard<T: TextViewImpl>(ptr: *mut ffi::GtkTextView)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<TextView>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -370,6 +400,8 @@ where
 unsafe extern "C" fn text_view_set_anchor<T: TextViewImpl>(ptr: *mut ffi::GtkTextView)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<TextView>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -383,6 +415,8 @@ unsafe extern "C" fn text_view_snapshot_layer<T: TextViewImpl>(
     snapshot: *mut ffi::GtkSnapshot,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<TextView>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -393,6 +427,8 @@ unsafe extern "C" fn text_view_snapshot_layer<T: TextViewImpl>(
 unsafe extern "C" fn text_view_toggle_overwrite<T: TextViewImpl>(ptr: *mut ffi::GtkTextView)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<TextView>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/toggle_button.rs b/gtk4/src/subclass/toggle_button.rs
index e632fbd8d268..04aecea402f9 100644
--- a/gtk4/src/subclass/toggle_button.rs
+++ b/gtk4/src/subclass/toggle_button.rs
@@ -5,11 +5,14 @@
 
 use glib::translate::*;
 
-use crate::{ffi, prelude::*, subclass::prelude::*, ToggleButton};
+use crate::{ffi, prelude::*, subclass::prelude::*, Button, ToggleButton, Widget};
 
 pub trait ToggleButtonImpl: ButtonImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Widget>,
+    <Self as ObjectSubclass>::Type: IsA<Button>,
+    <Self as ObjectSubclass>::Type: IsA<ToggleButton>,
 {
     fn toggled(&self) {
         self.parent_toggled()
@@ -19,6 +22,9 @@ where
 pub trait ToggleButtonImplExt: ToggleButtonImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Widget>,
+    <Self as ObjectSubclass>::Type: IsA<Button>,
+    <Self as ObjectSubclass>::Type: IsA<ToggleButton>,
 {
     fn parent_toggled(&self) {
         unsafe {
@@ -35,14 +41,21 @@ where
     }
 }
 
-impl<T: ToggleButtonImpl> ToggleButtonImplExt for T where
-    <T as ObjectSubclass>::Type: IsA<glib::Object>
+impl<T: ToggleButtonImpl> ToggleButtonImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Button>,
+    <T as ObjectSubclass>::Type: IsA<ToggleButton>,
 {
 }
 
 unsafe impl<T: ToggleButtonImpl> IsSubclassable<T> for ToggleButton
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Button>,
+    <T as ObjectSubclass>::Type: IsA<ToggleButton>,
 {
     fn class_init(class: &mut glib::Class<Self>) {
         Self::parent_class_init::<T>(class);
@@ -55,6 +68,9 @@ where
 unsafe extern "C" fn toggle_button_toggled<T: ToggleButtonImpl>(ptr: *mut ffi::GtkToggleButton)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Button>,
+    <T as ObjectSubclass>::Type: IsA<ToggleButton>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/tree_drag_dest.rs b/gtk4/src/subclass/tree_drag_dest.rs
index 0371517f386a..0803912e2b1c 100644
--- a/gtk4/src/subclass/tree_drag_dest.rs
+++ b/gtk4/src/subclass/tree_drag_dest.rs
@@ -13,6 +13,7 @@ use crate::{ffi, prelude::*, subclass::prelude::*, TreeDragDest, TreePath};
 pub trait TreeDragDestImpl: ObjectImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<TreeDragDest>,
 {
     fn drag_data_received(&self, dest: &TreePath, value: Value) -> bool;
     fn row_drop_possible(&self, dest: &TreePath, value: Value) -> bool;
@@ -23,6 +24,7 @@ where
 pub trait TreeDragDestImplExt: TreeDragDestImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<TreeDragDest>,
 {
     fn parent_drag_data_received(&self, dest: &TreePath, value: Value) -> bool {
         unsafe {
@@ -67,14 +69,17 @@ where
     }
 }
 
-impl<T: TreeDragDestImpl> TreeDragDestImplExt for T where
-    <T as ObjectSubclass>::Type: IsA<glib::Object>
+impl<T: TreeDragDestImpl> TreeDragDestImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<TreeDragDest>,
 {
 }
 
 unsafe impl<T: TreeDragDestImpl> IsImplementable<T> for TreeDragDest
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<TreeDragDest>,
 {
     fn interface_init(iface: &mut glib::Interface<Self>) {
         let iface = iface.as_mut();
@@ -93,6 +98,7 @@ unsafe extern "C" fn tree_drag_dest_drag_data_received<T: TreeDragDestImpl>(
 ) -> glib::ffi::gboolean
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<TreeDragDest>,
 {
     let instance = &*(tree_drag_dest as *mut T::Instance);
     let imp = instance.imp();
@@ -110,6 +116,7 @@ unsafe extern "C" fn tree_drag_dest_row_drop_possible<T: TreeDragDestImpl>(
 ) -> glib::ffi::gboolean
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<TreeDragDest>,
 {
     let instance = &*(tree_drag_dest as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/tree_drag_source.rs b/gtk4/src/subclass/tree_drag_source.rs
index 17cd9358228e..2bf210db5217 100644
--- a/gtk4/src/subclass/tree_drag_source.rs
+++ b/gtk4/src/subclass/tree_drag_source.rs
@@ -13,6 +13,7 @@ use crate::{ffi, prelude::*, subclass::prelude::*, TreeDragSource, TreePath};
 pub trait TreeDragSourceImpl: ObjectImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<TreeDragSource>,
 {
     fn row_draggable(&self, path: &TreePath) -> bool {
         self.parent_row_draggable(path)
@@ -26,6 +27,7 @@ where
 pub trait TreeDragSourceImplExt: TreeDragSourceImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<TreeDragSource>,
 {
     // Returns true if the row can be dragged
     fn parent_row_draggable(&self, path: &TreePath) -> bool {
@@ -91,14 +93,17 @@ where
     }
 }
 
-impl<T: TreeDragSourceImpl> TreeDragSourceImplExt for T where
-    <T as ObjectSubclass>::Type: IsA<glib::Object>
+impl<T: TreeDragSourceImpl> TreeDragSourceImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<TreeDragSource>,
 {
 }
 
 unsafe impl<T: TreeDragSourceImpl> IsImplementable<T> for TreeDragSource
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<TreeDragSource>,
 {
     fn interface_init(iface: &mut glib::Interface<Self>) {
         let iface = iface.as_mut();
@@ -117,6 +122,7 @@ unsafe extern "C" fn tree_drag_source_row_draggable<T: TreeDragSourceImpl>(
 ) -> glib::ffi::gboolean
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<TreeDragSource>,
 {
     let instance = &*(tree_drag_source as *mut T::Instance);
     let imp = instance.imp();
@@ -132,6 +138,7 @@ unsafe extern "C" fn tree_drag_source_drag_data_get<T: TreeDragSourceImpl>(
 ) -> *mut gdk::ffi::GdkContentProvider
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<TreeDragSource>,
 {
     let instance = &*(tree_drag_source as *mut T::Instance);
     let imp = instance.imp();
@@ -146,6 +153,7 @@ unsafe extern "C" fn tree_drag_source_drag_data_delete<T: TreeDragSourceImpl>(
 ) -> glib::ffi::gboolean
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<TreeDragSource>,
 {
     let instance = &*(tree_drag_source as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/tree_model_filter.rs b/gtk4/src/subclass/tree_model_filter.rs
index 96f2bc56c3c0..6b4afc6fb4bb 100644
--- a/gtk4/src/subclass/tree_model_filter.rs
+++ b/gtk4/src/subclass/tree_model_filter.rs
@@ -12,6 +12,7 @@ use crate::{ffi, prelude::*, subclass::prelude::*, TreeIter, TreeModel, TreeMode
 pub trait TreeModelFilterImpl: ObjectImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<TreeModelFilter>,
 {
     fn visible<M: IsA<TreeModel>>(&self, child_model: &M, iter: &TreeIter) -> bool {
         self.parent_visible(child_model, iter)
@@ -33,6 +34,7 @@ where
 pub trait TreeModelFilterImplExt: TreeModelFilterImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<TreeModelFilter>,
 {
     // Whether the row indicated by iter is visible
     fn parent_visible<M: IsA<TreeModel>>(&self, child_model: &M, iter: &TreeIter) -> bool {
@@ -80,14 +82,17 @@ where
     }
 }
 
-impl<T: TreeModelFilterImpl> TreeModelFilterImplExt for T where
-    <T as ObjectSubclass>::Type: IsA<glib::Object>
+impl<T: TreeModelFilterImpl> TreeModelFilterImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<TreeModelFilter>,
 {
 }
 
 unsafe impl<T: TreeModelFilterImpl> IsSubclassable<T> for TreeModelFilter
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<TreeModelFilter>,
 {
     fn class_init(class: &mut glib::Class<Self>) {
         Self::parent_class_init::<T>(class);
@@ -107,6 +112,7 @@ unsafe extern "C" fn tree_model_filter_visible<T: TreeModelFilterImpl>(
 ) -> glib::ffi::gboolean
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<TreeModelFilter>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -124,6 +130,7 @@ unsafe extern "C" fn tree_model_filter_modify<T: TreeModelFilterImpl>(
     column: i32,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<TreeModelFilter>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/tree_view.rs b/gtk4/src/subclass/tree_view.rs
index b9a7f9fae84c..8ef68dc205a6 100644
--- a/gtk4/src/subclass/tree_view.rs
+++ b/gtk4/src/subclass/tree_view.rs
@@ -7,7 +7,7 @@ use glib::translate::*;
 
 use crate::{
     ffi, prelude::*, subclass::prelude::*, MovementStep, TreeIter, TreePath, TreeView,
-    TreeViewColumn,
+    TreeViewColumn, Widget,
 };
 
 #[cfg_attr(feature = "v4_10", deprecated = "Since 4.10")]
@@ -15,6 +15,8 @@ use crate::{
 pub trait TreeViewImpl: WidgetImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Widget>,
+    <Self as ObjectSubclass>::Type: IsA<TreeView>,
 {
     fn columns_changed(&self) {
         self.parent_columns_changed()
@@ -82,6 +84,8 @@ where
 pub trait TreeViewImplExt: TreeViewImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Widget>,
+    <Self as ObjectSubclass>::Type: IsA<TreeView>,
 {
     fn parent_columns_changed(&self) {
         unsafe {
@@ -317,11 +321,19 @@ where
     }
 }
 
-impl<T: TreeViewImpl> TreeViewImplExt for T where <T as ObjectSubclass>::Type: IsA<glib::Object> {}
+impl<T: TreeViewImpl> TreeViewImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<TreeView>,
+{
+}
 
 unsafe impl<T: TreeViewImpl> IsSubclassable<T> for TreeView
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<TreeView>,
 {
     fn class_init(class: &mut glib::Class<Self>) {
         Self::parent_class_init::<T>(class);
@@ -348,6 +360,8 @@ where
 unsafe extern "C" fn tree_view_columns_changed<T: TreeViewImpl>(ptr: *mut ffi::GtkTreeView)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<TreeView>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -358,6 +372,8 @@ where
 unsafe extern "C" fn tree_view_cursor_changed<T: TreeViewImpl>(ptr: *mut ffi::GtkTreeView)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<TreeView>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -373,6 +389,8 @@ unsafe extern "C" fn tree_view_expand_collapse_cursor_row<T: TreeViewImpl>(
 ) -> glib::ffi::gboolean
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<TreeView>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -390,6 +408,8 @@ unsafe extern "C" fn tree_view_move_cursor<T: TreeViewImpl>(
 ) -> glib::ffi::gboolean
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<TreeView>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -404,6 +424,8 @@ unsafe extern "C" fn tree_view_row_activated<T: TreeViewImpl>(
     columnptr: *mut ffi::GtkTreeViewColumn,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<TreeView>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -419,6 +441,8 @@ unsafe extern "C" fn tree_view_row_collapsed<T: TreeViewImpl>(
     pathptr: *mut ffi::GtkTreePath,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<TreeView>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -434,6 +458,8 @@ unsafe extern "C" fn tree_view_row_expanded<T: TreeViewImpl>(
     pathptr: *mut ffi::GtkTreePath,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<TreeView>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -448,6 +474,8 @@ unsafe extern "C" fn tree_view_select_all<T: TreeViewImpl>(
 ) -> glib::ffi::gboolean
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<TreeView>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -460,6 +488,8 @@ unsafe extern "C" fn tree_view_select_cursor_parent<T: TreeViewImpl>(
 ) -> glib::ffi::gboolean
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<TreeView>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -473,6 +503,8 @@ unsafe extern "C" fn tree_view_select_cursor_row<T: TreeViewImpl>(
 ) -> glib::ffi::gboolean
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<TreeView>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -485,6 +517,8 @@ unsafe extern "C" fn tree_view_start_interactive_search<T: TreeViewImpl>(
 ) -> glib::ffi::gboolean
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<TreeView>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -499,6 +533,8 @@ unsafe extern "C" fn tree_view_test_collapse_row<T: TreeViewImpl>(
 ) -> glib::ffi::gboolean
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<TreeView>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -515,6 +551,8 @@ unsafe extern "C" fn tree_view_test_expand_row<T: TreeViewImpl>(
 ) -> glib::ffi::gboolean
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<TreeView>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -529,6 +567,8 @@ unsafe extern "C" fn tree_view_toggle_cursor_row<T: TreeViewImpl>(
 ) -> glib::ffi::gboolean
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<TreeView>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -541,6 +581,8 @@ unsafe extern "C" fn tree_view_unselect_all<T: TreeViewImpl>(
 ) -> glib::ffi::gboolean
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<TreeView>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/widget.rs b/gtk4/src/subclass/widget.rs
index b7e0935e6cd2..9599bb651129 100644
--- a/gtk4/src/subclass/widget.rs
+++ b/gtk4/src/subclass/widget.rs
@@ -104,9 +104,10 @@ impl Iterator for WidgetActionIter {
 
 impl std::iter::FusedIterator for WidgetActionIter {}
 
-pub trait WidgetImpl: WidgetImplExt + ObjectImpl
+pub trait WidgetImpl: ObjectImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Widget>,
 {
     fn compute_expand(&self, hexpand: &mut bool, vexpand: &mut bool) {
         self.parent_compute_expand(hexpand, vexpand)
@@ -210,12 +211,11 @@ where
     }
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::WidgetImplExt> Sealed for T {}
-}
-
-pub trait WidgetImplExt: sealed::Sealed + ObjectSubclass {
+pub trait WidgetImplExt: WidgetImpl
+where
+    <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Widget>,
+{
     fn parent_compute_expand(&self, hexpand: &mut bool, vexpand: &mut bool) {
         unsafe {
             let data = Self::type_data();
@@ -553,11 +553,17 @@ pub trait WidgetImplExt: sealed::Sealed + ObjectSubclass {
     }
 }
 
-impl<T: WidgetImpl> WidgetImplExt for T where <T as ObjectSubclass>::Type: IsA<glib::Object> {}
+impl<T: WidgetImpl> WidgetImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+{
+}
 
 unsafe impl<T: WidgetImpl> IsSubclassable<T> for Widget
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
 {
     fn class_init(class: &mut ::glib::Class<Self>) {
         Self::parent_class_init::<T>(class);
@@ -605,6 +611,7 @@ unsafe extern "C" fn widget_compute_expand<T: WidgetImpl>(
     vexpand_ptr: *mut glib::ffi::gboolean,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -635,6 +642,7 @@ unsafe extern "C" fn widget_contains<T: WidgetImpl>(
 ) -> glib::ffi::gboolean
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -647,6 +655,7 @@ unsafe extern "C" fn widget_direction_changed<T: WidgetImpl>(
     direction_ptr: ffi::GtkTextDirection,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -661,6 +670,7 @@ unsafe extern "C" fn widget_focus<T: WidgetImpl>(
 ) -> glib::ffi::gboolean
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -674,6 +684,7 @@ unsafe extern "C" fn widget_get_request_mode<T: WidgetImpl>(
 ) -> ffi::GtkSizeRequestMode
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -686,6 +697,7 @@ unsafe extern "C" fn widget_grab_focus<T: WidgetImpl>(
 ) -> glib::ffi::gboolean
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -696,6 +708,7 @@ where
 unsafe extern "C" fn widget_hide<T: WidgetImpl>(ptr: *mut ffi::GtkWidget)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -709,6 +722,7 @@ unsafe extern "C" fn widget_keynav_failed<T: WidgetImpl>(
 ) -> glib::ffi::gboolean
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -720,6 +734,7 @@ where
 unsafe extern "C" fn widget_map<T: WidgetImpl>(ptr: *mut ffi::GtkWidget)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -737,6 +752,7 @@ unsafe extern "C" fn widget_measure<T: WidgetImpl>(
     nat_base_ptr: *mut libc::c_int,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -762,6 +778,7 @@ unsafe extern "C" fn widget_mnemonic_activate<T: WidgetImpl>(
 ) -> glib::ffi::gboolean
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -775,6 +792,7 @@ unsafe extern "C" fn widget_move_focus<T: WidgetImpl>(
     direction_type_ptr: ffi::GtkDirectionType,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -792,6 +810,7 @@ unsafe extern "C" fn widget_query_tooltip<T: WidgetImpl>(
 ) -> glib::ffi::gboolean
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -806,6 +825,7 @@ where
 unsafe extern "C" fn widget_realize<T: WidgetImpl>(ptr: *mut ffi::GtkWidget)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -816,6 +836,7 @@ where
 unsafe extern "C" fn widget_root<T: WidgetImpl>(ptr: *mut ffi::GtkWidget)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -828,6 +849,7 @@ unsafe extern "C" fn widget_set_focus_child<T: WidgetImpl>(
     child_ptr: *mut ffi::GtkWidget,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -839,6 +861,7 @@ unsafe extern "C" fn widget_set_focus_child<T: WidgetImpl>(
 unsafe extern "C" fn widget_show<T: WidgetImpl>(ptr: *mut ffi::GtkWidget)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -853,6 +876,7 @@ unsafe extern "C" fn widget_size_allocate<T: WidgetImpl>(
     baseline: i32,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -865,6 +889,7 @@ unsafe extern "C" fn widget_snapshot<T: WidgetImpl>(
     snapshot_ptr: *mut ffi::GtkSnapshot,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -878,6 +903,7 @@ unsafe extern "C" fn widget_state_flags_changed<T: WidgetImpl>(
     state_flags_ptr: ffi::GtkStateFlags,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -891,6 +917,7 @@ unsafe extern "C" fn widget_system_setting_changed<T: WidgetImpl>(
     settings_ptr: ffi::GtkSystemSetting,
 ) where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -902,6 +929,7 @@ unsafe extern "C" fn widget_system_setting_changed<T: WidgetImpl>(
 unsafe extern "C" fn widget_unmap<T: WidgetImpl>(ptr: *mut ffi::GtkWidget)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -912,6 +940,7 @@ where
 unsafe extern "C" fn widget_unrealize<T: WidgetImpl>(ptr: *mut ffi::GtkWidget)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -922,6 +951,7 @@ where
 unsafe extern "C" fn widget_unroot<T: WidgetImpl>(ptr: *mut ffi::GtkWidget)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -1284,8 +1314,9 @@ pub unsafe trait WidgetClassExt: ClassStruct {
 
 unsafe impl<T: ClassStruct> WidgetClassExt for T
 where
-    <T::Type as ObjectSubclass>::Type: IsA<glib::Object>,
     T::Type: WidgetImpl,
+    <T::Type as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T::Type as ObjectSubclass>::Type: IsA<Widget>,
 {
 }
 
@@ -1392,6 +1423,7 @@ where
 pub trait CompositeTemplate: WidgetImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Widget>,
 {
     fn bind_template(klass: &mut Self::Class);
     fn check_template_children(widget: &<Self as ObjectSubclass>::Type);
@@ -1413,6 +1445,7 @@ where
     T: ClassStruct<Type = U>,
     U: ObjectSubclass<Class = T> + CompositeTemplate,
     <U as ObjectSubclass>::Type: IsA<glib::Object>,
+    <U as ObjectSubclass>::Type: IsA<Widget>,
 {
     fn bind_template(&mut self) {
         <U as CompositeTemplate>::bind_template(self);
diff --git a/gtk4/src/subclass/window.rs b/gtk4/src/subclass/window.rs
index 25972e7c09b7..b2b831b8dcff 100644
--- a/gtk4/src/subclass/window.rs
+++ b/gtk4/src/subclass/window.rs
@@ -5,11 +5,13 @@
 
 use glib::translate::*;
 
-use crate::{ffi, prelude::*, subclass::prelude::*, Window};
+use crate::{ffi, prelude::*, subclass::prelude::*, Widget, Window};
 
 pub trait WindowImpl: WidgetImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Widget>,
+    <Self as ObjectSubclass>::Type: IsA<Window>,
 {
     fn activate_focus(&self) {
         self.parent_activate_focus()
@@ -35,6 +37,8 @@ where
 pub trait WindowImplExt: WindowImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<Widget>,
+    <Self as ObjectSubclass>::Type: IsA<Window>,
 {
     fn parent_activate_focus(&self) {
         unsafe {
@@ -96,11 +100,19 @@ where
     }
 }
 
-impl<T: WindowImpl> WindowImplExt for T where <T as ObjectSubclass>::Type: IsA<glib::Object> {}
+impl<T: WindowImpl> WindowImplExt for T
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Window>,
+{
+}
 
 unsafe impl<T: WindowImpl> IsSubclassable<T> for Window
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Window>,
 {
     fn class_init(class: &mut ::glib::Class<Self>) {
         Self::parent_class_init::<T>(class);
@@ -117,6 +129,8 @@ where
 unsafe extern "C" fn window_activate_focus<T: WindowImpl>(ptr: *mut ffi::GtkWindow)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Window>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -127,6 +141,8 @@ where
 unsafe extern "C" fn window_activate_default<T: WindowImpl>(ptr: *mut ffi::GtkWindow)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Window>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -137,6 +153,8 @@ where
 unsafe extern "C" fn window_keys_changed<T: WindowImpl>(ptr: *mut ffi::GtkWindow)
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Window>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -150,6 +168,8 @@ unsafe extern "C" fn window_enable_debugging<T: WindowImpl>(
 ) -> glib::ffi::gboolean
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Window>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
@@ -163,6 +183,8 @@ unsafe extern "C" fn window_close_request<T: WindowImpl>(
 ) -> glib::ffi::gboolean
 where
     <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<Widget>,
+    <T as ObjectSubclass>::Type: IsA<Window>,
 {
     let instance = &*(ptr as *mut T::Instance);
     let imp = instance.imp();
diff --git a/gtk4/src/subclass/window_group.rs b/gtk4/src/subclass/window_group.rs
index 2d9dfb1f598f..b22cce4da751 100644
--- a/gtk4/src/subclass/window_group.rs
+++ b/gtk4/src/subclass/window_group.rs
@@ -8,10 +8,13 @@ use crate::{prelude::*, subclass::prelude::*, WindowGroup};
 pub trait WindowGroupImpl: ObjectImpl
 where
     <Self as ObjectSubclass>::Type: IsA<glib::Object>,
+    <Self as ObjectSubclass>::Type: IsA<WindowGroup>,
 {
 }
 
-unsafe impl<T: WindowGroupImpl> IsSubclassable<T> for WindowGroup where
-    <T as ObjectSubclass>::Type: IsA<glib::Object>
+unsafe impl<T: WindowGroupImpl> IsSubclassable<T> for WindowGroup
+where
+    <T as ObjectSubclass>::Type: IsA<glib::Object>,
+    <T as ObjectSubclass>::Type: IsA<WindowGroup>,
 {
 }