diff --git a/code/AdminErrorExtension.php b/code/AdminErrorExtension.php
index f8d38e160..a72a51821 100644
--- a/code/AdminErrorExtension.php
+++ b/code/AdminErrorExtension.php
@@ -16,7 +16,7 @@ class AdminErrorExtension extends Extension
     /**
      * Used by {@see RequestHandler::httpError}
      */
-    public function onBeforeHTTPError($statusCode, HTTPRequest $request, $errorMessage = null)
+    protected function onBeforeHTTPError($statusCode, HTTPRequest $request, $errorMessage = null)
     {
         $controller = $this->getAdminController();
         if (!$controller || Director::is_ajax($request) || $errorMessage === null) {
diff --git a/code/Forms/GridFieldDetailFormPreviewExtension.php b/code/Forms/GridFieldDetailFormPreviewExtension.php
index a821614ed..68d87c346 100644
--- a/code/Forms/GridFieldDetailFormPreviewExtension.php
+++ b/code/Forms/GridFieldDetailFormPreviewExtension.php
@@ -17,7 +17,7 @@
  */
 class GridFieldDetailFormPreviewExtension extends Extension
 {
-    public function updateItemEditForm(Form $form): void
+    protected function updateItemEditForm(Form $form): void
     {
         $record = $this->owner->getRecord();
         // See LeftAndMain::getEditForm()
diff --git a/code/Forms/GridFieldPrintButtonExtension.php b/code/Forms/GridFieldPrintButtonExtension.php
index ccd48f874..9e808ae92 100644
--- a/code/Forms/GridFieldPrintButtonExtension.php
+++ b/code/Forms/GridFieldPrintButtonExtension.php
@@ -11,7 +11,7 @@
  */
 class GridFieldPrintButtonExtension extends Extension
 {
-    public function updatePrintData($data)
+    protected function updatePrintData($data)
     {
         Requirements::css('silverstripe/admin:client/dist/styles/GridField_print.css');
     }
diff --git a/code/Forms/UsedOnTable.php b/code/Forms/UsedOnTable.php
index ea5ef2108..0521d3a35 100644
--- a/code/Forms/UsedOnTable.php
+++ b/code/Forms/UsedOnTable.php
@@ -83,7 +83,7 @@ public function usage(HTTPRequest $request)
             // Legacy extension hook kept for backwards compatibility
             // Use 'updateUsageExcludedClasses' extension hook instead which prevents database from being queried
             //
-            // Example: public function updateUsage(ArrayList &$usage, DataObject &$record)
+            // Example: protected function updateUsage(ArrayList &$usage, DataObject &$record)
             //     $dataObjects = $usage->exclude('ClassName', MyDataObject::class);
             $this->extend('updateUsage', $usage, $record);
         }
diff --git a/code/LeftAndMainExtension.php b/code/LeftAndMainExtension.php
index 62835f1e4..a13037656 100644
--- a/code/LeftAndMainExtension.php
+++ b/code/LeftAndMainExtension.php
@@ -17,11 +17,11 @@ public function init()
     {
     }
 
-    public function accessedCMS()
+    protected function accessedCMS()
     {
     }
 
-    public function augmentNewSiteTreeItem(&$item)
+    protected function augmentNewSiteTreeItem(&$item)
     {
     }
 }
diff --git a/code/ModelAdmin.php b/code/ModelAdmin.php
index 5af2b9c1c..6e9158757 100644
--- a/code/ModelAdmin.php
+++ b/code/ModelAdmin.php
@@ -381,7 +381,7 @@ public function getExportFields()
      * Archived flag is set to false. That would be best done as an extension, for example:
      *
      * <code>
-     * public function updateList(\SilverStripe\ORM\DataList $list)
+     * protected function updateList(\SilverStripe\ORM\DataList $list)
      * {
      *     return $list->filter('Archived', false);
      * }
diff --git a/tests/behat/src/Extension/MemberEmailLinkExtension.php b/tests/behat/src/Extension/MemberEmailLinkExtension.php
index d2e6d22ec..db09690ab 100644
--- a/tests/behat/src/Extension/MemberEmailLinkExtension.php
+++ b/tests/behat/src/Extension/MemberEmailLinkExtension.php
@@ -15,7 +15,7 @@
  */
 class MemberEmailLinkExtension extends Extension implements TestOnly
 {
-    public function updateGridField(GridField $gridField)
+    protected function updateGridField(GridField $gridField)
     {
         if (is_a($this->getOwner()->getModelClass(), Member::class, true)) {
             $columns = $gridField->getConfig()->getComponentByType(GridFieldDataColumns::class);
diff --git a/tests/php/ModelAdminTest/ModelAdminExtension.php b/tests/php/ModelAdminTest/ModelAdminExtension.php
index 384f79050..94ce4d25f 100644
--- a/tests/php/ModelAdminTest/ModelAdminExtension.php
+++ b/tests/php/ModelAdminTest/ModelAdminExtension.php
@@ -15,13 +15,13 @@
 class ModelAdminExtension extends Extension implements TestOnly
 {
 
-    public function updateGridField(GridField &$field)
+    protected function updateGridField(GridField &$field)
     {
         $this->getOwner()->calls[__FUNCTION__]++;
         $field->setAttribute('ModelAdminExtension', 'called');
     }
 
-    public function updateGridFieldConfig(GridFieldConfig &$config)
+    protected function updateGridFieldConfig(GridFieldConfig &$config)
     {
         $this->getOwner()->calls[__FUNCTION__]++;
         $config->removeComponentsByType(GridFieldExportButton::class);
diff --git a/tests/php/UsedOnTableTest/ExtTest_Extension.php b/tests/php/UsedOnTableTest/ExtTest_Extension.php
index 46208b04f..46f8f3f5e 100644
--- a/tests/php/UsedOnTableTest/ExtTest_Extension.php
+++ b/tests/php/UsedOnTableTest/ExtTest_Extension.php
@@ -9,12 +9,12 @@
 class ExtTest_Extension extends Extension implements TestOnly
 {
 
-    public function updateUsageExcludedClasses(array &$excludedClasses)
+    protected function updateUsageExcludedClasses(array &$excludedClasses)
     {
         $excludedClasses[] = ExtTest_Middle::class;
     }
 
-    public function updateUsageAncestorDataObjects(array &$ancestorDataObjects, DataObject $dataObject)
+    protected function updateUsageAncestorDataObjects(array &$ancestorDataObjects, DataObject $dataObject)
     {
         if (!($dataObject instanceof ExtTest_Outer)) {
             return;