diff --git a/src/Extensions/MenuSetParentExtension.php b/src/Extensions/MenuSetParentExtension.php
index 59b5672..0af1c1e 100644
--- a/src/Extensions/MenuSetParentExtension.php
+++ b/src/Extensions/MenuSetParentExtension.php
@@ -31,6 +31,10 @@ class MenuSetParentExtension extends DataExtension
         'MenuSets'
     ];
 
+    private static $cascade_duplicates = [
+        'MenuSets'
+    ];
+
     public function updateCMSFields(FieldList $fields)
     {
         $fields->removeByName('MenuSets');
diff --git a/src/Model/MenuItem.php b/src/Model/MenuItem.php
index 25d3a5a..2d06e47 100644
--- a/src/Model/MenuItem.php
+++ b/src/Model/MenuItem.php
@@ -70,6 +70,10 @@ class MenuItem extends SuperLink
         'Children'
     ];
 
+    private static $cascade_duplicates = [
+        'Children'
+    ];
+
     private static $field_labels = [
         'SubmenuMode' => 'Submenu',
         'SubmenuSiteTree' => 'Select Page'
diff --git a/src/Model/MenuSet.php b/src/Model/MenuSet.php
index 5d8ddcb..5c36395 100644
--- a/src/Model/MenuSet.php
+++ b/src/Model/MenuSet.php
@@ -59,6 +59,10 @@ class MenuSet extends DataObject
         'Items'
     ];
 
+    private static $cascade_duplicates = [
+        'Items'
+    ];
+
     private static $defaults = [
         'IsTitleEnabled' => false,
         'IsHighlightEnabled' => false,