diff --git a/lib/private/Group/Manager.php b/lib/private/Group/Manager.php
index 2d40b44799695..a0d7bf0819da6 100644
--- a/lib/private/Group/Manager.php
+++ b/lib/private/Group/Manager.php
@@ -323,7 +323,7 @@ public function isInGroup($userId, $group) {
 	 * @param IUser $user
 	 * @return array with group ids
 	 */
-	public function getUserGroupIds(IUser $user) {
+	public function getUserGroupIds(IUser $user = null) {
 		return array_map(function($value) {
 			return (string) $value;
 		}, array_keys($this->getUserGroups($user)));