diff --git a/code/AdminErrorExtension.php b/code/AdminErrorExtension.php
index ba961befe..f8d38e160 100644
--- a/code/AdminErrorExtension.php
+++ b/code/AdminErrorExtension.php
@@ -5,8 +5,12 @@
 use SilverStripe\Control\Controller;
 use SilverStripe\Control\Director;
 use SilverStripe\Control\HTTPRequest;
+use SilverStripe\Control\RequestHandler;
 use SilverStripe\Core\Extension;
 
+/**
+ * @extends Extension<RequestHandler>
+ */
 class AdminErrorExtension extends Extension
 {
     /**
diff --git a/code/CMSEditLinkExtension.php b/code/CMSEditLinkExtension.php
index 31e32f2d3..ce20bce31 100644
--- a/code/CMSEditLinkExtension.php
+++ b/code/CMSEditLinkExtension.php
@@ -32,6 +32,9 @@
  *
  * If the cms_edit_owner is a has_one relation, the class on the other end
  * of the relation must have a CMSEditLink() method.
+ *
+ * @template T of LeftAndMain|DataObject
+ * @extends Extension<T&static>
  */
 class CMSEditLinkExtension extends Extension
 {
@@ -40,7 +43,7 @@ class CMSEditLinkExtension extends Extension
     /**
      * Get the ModelAdmin, LeftAndMain, or DataObject which owns this object for CMS editing purposes.
      *
-     * @return LeftAndMain|DataObject|null
+     * @return DataObject|LeftAndMain|null
      */
     public function getCMSEditOwner()
     {
@@ -71,6 +74,7 @@ public function getCMSEditLinkForManagedDataObject(DataObject $obj, string $reci
      */
     public function CMSEditLink(): string
     {
+        /** @var DataObject|LeftAndMain|null $owner */
         $owner = $this->owner->getCMSEditOwner();
         if (!$owner || !$owner->exists()) {
             return '';
diff --git a/code/Forms/GridFieldDetailFormPreviewExtension.php b/code/Forms/GridFieldDetailFormPreviewExtension.php
index ba1ac4747..a821614ed 100644
--- a/code/Forms/GridFieldDetailFormPreviewExtension.php
+++ b/code/Forms/GridFieldDetailFormPreviewExtension.php
@@ -6,11 +6,15 @@
 use SilverStripe\Admin\Navigator\SilverStripeNavigator;
 use SilverStripe\Core\Extension;
 use SilverStripe\Forms\Form;
+use SilverStripe\Forms\GridField\GridFieldDetailForm_ItemRequest;
 use SilverStripe\Forms\LiteralField;
 use SilverStripe\ORM\CMSPreviewable;
 use SilverStripe\ORM\FieldType\DBHTMLText;
 use SilverStripe\View\SSViewer;
 
+/**
+ * @extends Extension<GridFieldDetailForm_ItemRequest>
+ */
 class GridFieldDetailFormPreviewExtension extends Extension
 {
     public function updateItemEditForm(Form $form): void
diff --git a/code/Forms/GridFieldPrintButtonExtension.php b/code/Forms/GridFieldPrintButtonExtension.php
index ecfb2123e..ccd48f874 100644
--- a/code/Forms/GridFieldPrintButtonExtension.php
+++ b/code/Forms/GridFieldPrintButtonExtension.php
@@ -3,8 +3,12 @@
 namespace SilverStripe\Admin\Forms;
 
 use SilverStripe\Core\Extension;
+use SilverStripe\Forms\GridField\GridFieldPrintButton;
 use SilverStripe\View\Requirements;
 
+/**
+ * @extends Extension<GridFieldPrintButton>
+ */
 class GridFieldPrintButtonExtension extends Extension
 {
     public function updatePrintData($data)
diff --git a/code/LeftAndMainExtension.php b/code/LeftAndMainExtension.php
index 2980c03e7..3fc16e544 100644
--- a/code/LeftAndMainExtension.php
+++ b/code/LeftAndMainExtension.php
@@ -6,6 +6,9 @@
 
 /**
  * Plug-ins for additional functionality in your LeftAndMain classes.
+ *
+ * @template T of DataObject
+ * @extends Extension<T>
  */
 abstract class LeftAndMainExtension extends Extension
 {