diff --git a/code/extensions/LeftAndMainSubsites.php b/code/extensions/LeftAndMainSubsites.php
index 9079b41c..51887bf5 100644
--- a/code/extensions/LeftAndMainSubsites.php
+++ b/code/extensions/LeftAndMainSubsites.php
@@ -348,12 +348,11 @@ public function onAfterSave($record)
 
     /**
      * @param array $data
-     * @param Form $form
      */
-    public function copytosubsite($data, $form)
+    public function copytosubsite($data)
     {
-        $page = DataObject::get_by_id(SiteTree::class, $data['ID']);
-        $subsite = DataObject::get_by_id('Subsite', $data['CopyToSubsiteID']);
+        $page = SiteTree::get()->byID($data['ID']);
+        $subsite = Subsite::get()->byID($data['CopyToSubsiteID']);
         $includeChildren = isset($data['CopyToSubsiteWithChildren']) ? $data['CopyToSubsiteWithChildren'] : false;
 
         $newPage = $page->duplicateToSubsite($subsite->ID, $includeChildren);
diff --git a/code/extensions/SiteTreeSubsites.php b/code/extensions/SiteTreeSubsites.php
index f281a19f..5a450ed0 100644
--- a/code/extensions/SiteTreeSubsites.php
+++ b/code/extensions/SiteTreeSubsites.php
@@ -12,7 +12,7 @@
 use SilverStripe\Forms\CheckboxField;
 use SilverStripe\Forms\DropdownField;
 use SilverStripe\Forms\FieldList;
-use SilverStripe\Forms\InlineFormAction;
+use SilverStripe\Forms\FormAction;
 use SilverStripe\Forms\ToggleCompositeField;
 use SilverStripe\ORM\DataExtension;
 use SilverStripe\ORM\DataObject;
@@ -109,7 +109,7 @@ public function updateCMSFields(FieldList $fields)
         $isDefaultSubsite = $this->owner->SubsiteID == 0 || $this->owner->Subsite()->DefaultSite;
 
         if ($isDefaultSubsite && $subsitesMap) {
-            $fields->addFieldsToTab(
+            $fields->addFieldToTab(
                 'Root.Main',
                 ToggleCompositeField::create('SubsiteOperations',
                     _t('SiteTreeSubsites.SubsiteOperations', 'Subsite Operations'),
@@ -118,7 +118,7 @@ public function updateCMSFields(FieldList $fields)
                             'Copy page to subsite'), $subsitesMap),
                         new CheckboxField('CopyToSubsiteWithChildren',
                             _t('SiteTreeSubsites.CopyToSubsiteWithChildren', 'Include children pages?')),
-                        $copyAction = new InlineFormAction(
+                        $copyAction = new FormAction(
                             'copytosubsite',
                             _t('SiteTreeSubsites.CopyAction', 'Copy')
                         )