diff --git a/src/Services/Sources.php b/src/Services/Sources.php
index 1db2a8a8..3e387d99 100644
--- a/src/Services/Sources.php
+++ b/src/Services/Sources.php
@@ -110,6 +110,10 @@ public function getSource($fieldType, $source, $indexFrom, $indexTo)
               break;
           case 'editLocale':
               return $source;
+          case 'assignUserGroup':
+              $service = Craft::app()->userGroups;
+              $method = 'getGroupBy';
+              break;
        }
 
        if (isset($service) && isset($method) && isset($sourceFrom)) {