diff --git a/classes/Gems/Default/StaffAction.php b/classes/Gems/Default/StaffAction.php
index <HASH>..<HASH> 100644
--- a/classes/Gems/Default/StaffAction.php
+++ b/classes/Gems/Default/StaffAction.php
@@ -129,6 +129,14 @@ class Gems_Default_StaffAction extends Gems_Controller_BrowseEditAction
         //@@TODO: Think of a better way to allow multiple methods per organization

         if ($this->escort->hasPrivilege('pr.staff.edit.all')) {

             $model->set('gul_user_class', 'label', $this->_('User Definition'));

+            

+            //Make sure old or experimental userdefinitions don't have to be changed to something that is

+            //allowed at the moment. For example the oldStaffUser can stay when editing a user.

+            $options = $model->get('gul_user_class', 'multiOptions');

+            if (!array_key_exists($data['gul_user_class'], $options)) {

+                $options[$data['gul_user_class']] = $this->_('Unsupported UserDefinition');

+                $model->set('gul_user_class', 'multiOptions', $options);

+            }

             $bridge->add('gul_user_class');

         } else {

             $bridge->addHidden('gul_user_class');
Fix to prevent change of userclass while editing of users with a UserDefinition that is not yet or no longer supported like the OldStaffUSerDefinition