diff --git a/mknodes/navs/mkdoc.py b/mknodes/navs/mkdoc.py
index de8b7693..3beb61b0 100644
--- a/mknodes/navs/mkdoc.py
+++ b/mknodes/navs/mkdoc.py
@@ -1,7 +1,6 @@
 from __future__ import annotations
 
 from collections.abc import Callable, Iterator, Sequence
-import inspect
 import types
 
 from typing import Any
@@ -94,11 +93,10 @@ def _collect_classes(self):
 
     def iter_classes(
         self,
-        submodule: types.ModuleType | str | tuple | list | None = None,
+        submodule: types.ModuleType | str | tuple[str, ...] | list[str] | None = None,
         *,
         recursive: bool = False,
         predicate: Callable[[type], bool] | None = None,
-        _seen: set | None = None,
     ) -> Iterator[type]:
         """Iterate over all classes of the module.
 
@@ -108,33 +106,16 @@ def iter_classes(
                        or whether it should also include classes from submodules.
             predicate: filter classes based on a predicate.
         """
-        if isinstance(submodule, list):
-            submodule = tuple(submodule)
-        mod = classhelpers.to_module(submodule) if submodule else self.module
-        if mod is None:
+        module = submodule or self.module
+        if module is None:
             return
-        if recursive:
-            seen = _seen or set()
-            # TODO: pkgutil.iter_modules would also list "unknown" modules
-            for submod in classhelpers.get_submodules(mod):
-                if submod not in seen:
-                    seen.add(submod)
-                    yield from self.iter_classes(
-                        submod,
-                        recursive=True,
-                        predicate=predicate,
-                        _seen=seen,
-                    )
-        for klass_name, klass in inspect.getmembers(mod, inspect.isclass):
-            if self.filter_by___all__ and (
-                not hasattr(mod, "__all__") or klass_name not in mod.__all__
-            ):
-                continue
-            if predicate and not predicate(klass):
-                continue
-            # if klass.__module__.startswith(self.module_name):
-            if self.module_name in klass.__module__.split("."):
-                yield klass
+        yield from classhelpers.list_classes(
+            module=tuple(module) if isinstance(module, list) else module,
+            recursive=recursive,
+            filter_by___all__=self.filter_by___all__,
+            predicate=predicate,
+            module_filter=self.module_name,
+        )
 
     def add_class_page(
         self,
diff --git a/mknodes/utils/classhelpers.py b/mknodes/utils/classhelpers.py
index df257e10..f99bb611 100644
--- a/mknodes/utils/classhelpers.py
+++ b/mknodes/utils/classhelpers.py
@@ -267,6 +267,7 @@ def list_classes(
     type_filter: type | None | types.UnionType = None,
     module_filter: str | None = None,
     filter_by___all__: bool = False,
+    predicate: Callable[[type], bool] | None = None,
     recursive: bool = False,
 ) -> list[type]:
     """Return list of classes from given module.
@@ -277,6 +278,7 @@ def list_classes(
         type_filter: only return classes which are subclasses of given type.
         module_filter: filter by a module prefix.
         filter_by___all__: Whether to filter based on whats defined in __all__.
+        predicate: filter classes based on a predicate.
         recursive: import all submodules recursively and also return their classes.
     """
     return list(
@@ -285,6 +287,7 @@ def list_classes(
             type_filter=type_filter,
             module_filter=module_filter,
             filter_by___all__=filter_by___all__,
+            predicate=predicate,
             recursive=recursive,
         )
     )
@@ -296,7 +299,9 @@ def iter_classes(
     type_filter: type | None | types.UnionType = None,
     module_filter: str | None = None,
     filter_by___all__: bool = False,
+    predicate: Callable[[type], bool] | None = None,
     recursive: bool = False,
+    # _seen: set | None = None,
 ) -> Iterator[type]:
     """Yield classes from given module.
 
@@ -306,25 +311,32 @@ def iter_classes(
         type_filter: only yield classes which are subclasses of given type.
         module_filter: filter by a module prefix.
         filter_by___all__: Whether to filter based on whats defined in __all__.
+        predicate: filter classes based on a predicate.
         recursive: import all submodules recursively and also yield their classes.
     """
     mod = to_module(module)
     if not mod:
         return []
     if recursive:
+        # seen = _seen or set()
         for submod in get_submodules(mod):
+            # if submod not in seen:
+            #     seen.add(submod)
             if submod.__name__.startswith(module_filter or ""):
                 yield from iter_classes(
                     submod,
                     type_filter=type_filter,
                     module_filter=submod.__name__,
                     filter_by___all__=filter_by___all__,
+                    predicate=predicate,
                     recursive=True,
                 )
     for klass_name, kls in get_members(mod, inspect.isclass):
         has_all = hasattr(mod, "__all__")
         if filter_by___all__ and (not has_all or klass_name not in mod.__all__):
             continue
+        if predicate and not predicate(kls):
+            continue
         if type_filter is not None and not issubclass(kls, type_filter):
             continue
         if module_filter is not None and not kls.__module__.startswith(module_filter):