diff --git a/src/Extension/FluentExtension.php b/src/Extension/FluentExtension.php
index bde51b28..36743961 100644
--- a/src/Extension/FluentExtension.php
+++ b/src/Extension/FluentExtension.php
@@ -463,7 +463,7 @@ protected function augmentDatabaseRequireTable($localisedTable, $fields, $indexe
         DB::require_table($localisedTable, $fields, $indexes, false);
     }
 
-    protected function augmentSQL(SQLSelect $query, DataQuery $dataQuery = null)
+    protected function augmentSQL(SQLSelect $query, ?DataQuery $dataQuery = null)
     {
         $locale = $this->getDataQueryLocale($dataQuery);
         if (!$locale) {
@@ -937,7 +937,7 @@ protected function localiseCondition($table, $field, Locale $locale)
      * @param DataQuery $dataQuery
      * @return Locale|null
      */
-    protected function getDataQueryLocale(DataQuery $dataQuery = null)
+    protected function getDataQueryLocale(?DataQuery $dataQuery = null)
     {
         if (!$dataQuery) {
             return null;
diff --git a/src/Extension/FluentFilteredExtension.php b/src/Extension/FluentFilteredExtension.php
index 944391f1..8fb06348 100644
--- a/src/Extension/FluentFilteredExtension.php
+++ b/src/Extension/FluentFilteredExtension.php
@@ -101,7 +101,7 @@ public function isAvailableInLocale($locale = null)
      * @param SQLSelect      $query
      * @param DataQuery|null $dataQuery
      */
-    protected function augmentSQL(SQLSelect $query, DataQuery $dataQuery = null)
+    protected function augmentSQL(SQLSelect $query, ?DataQuery $dataQuery = null)
     {
         // We don't want this logic applied in the CMS.
         if (!FluentState::singleton()->getIsFrontend()) {
@@ -138,7 +138,7 @@ protected function augmentSQL(SQLSelect $query, DataQuery $dataQuery = null)
      * @param DataQuery $dataQuery
      * @return Locale|null
      */
-    protected function getDataQueryLocale(DataQuery $dataQuery = null)
+    protected function getDataQueryLocale(?DataQuery $dataQuery = null)
     {
         if (!$dataQuery) {
             return null;
diff --git a/src/Extension/FluentIsolatedExtension.php b/src/Extension/FluentIsolatedExtension.php
index 6348460d..e167c126 100644
--- a/src/Extension/FluentIsolatedExtension.php
+++ b/src/Extension/FluentIsolatedExtension.php
@@ -79,7 +79,7 @@ protected function onRequireDefaultRecords()
      * @param SQLSelect $query
      * @param DataQuery|null $dataQuery
      */
-    protected function augmentSQL(SQLSelect $query, DataQuery $dataQuery = null)
+    protected function augmentSQL(SQLSelect $query, ?DataQuery $dataQuery = null)
     {
         $locale = $this->getDataQueryLocale($dataQuery);
         if (!$locale) {
@@ -114,7 +114,7 @@ protected function augmentSQL(SQLSelect $query, DataQuery $dataQuery = null)
      * @param DataQuery $dataQuery
      * @return Locale|null
      */
-    protected function getDataQueryLocale(DataQuery $dataQuery = null)
+    protected function getDataQueryLocale(?DataQuery $dataQuery = null)
     {
         if (!$dataQuery) {
             return null;
diff --git a/src/Extension/FluentVersionedExtension.php b/src/Extension/FluentVersionedExtension.php
index 7849e2b5..63ec14b0 100644
--- a/src/Extension/FluentVersionedExtension.php
+++ b/src/Extension/FluentVersionedExtension.php
@@ -155,7 +155,7 @@ protected function augmentDatabaseRequireTable($localisedTable, $fields, $indexe
      *
      * @throws InvalidArgumentException if an invalid versioned mode is provided
      */
-    protected function augmentSQL(SQLSelect $query, DataQuery $dataQuery = null)
+    protected function augmentSQL(SQLSelect $query, ?DataQuery $dataQuery = null)
     {
         $locale = $this->getDataQueryLocale($dataQuery);
         if (!$locale) {
@@ -802,7 +802,7 @@ public function isArchivedInLocale(?string $locale = null): ?bool
      * @param string|null $locale
      * @return bool|null
      */
-    public function hasArchiveInLocale(string $locale = null): ?bool
+    public function hasArchiveInLocale(?string $locale = null): ?bool
     {
         $locale = $locale ?: FluentState::singleton()->getLocale();