diff --git a/phpgwapi/inc/class.groupdav_principals.inc.php b/phpgwapi/inc/class.groupdav_principals.inc.php
index 9daba79dfa..f4a8813a7b 100644
--- a/phpgwapi/inc/class.groupdav_principals.inc.php
+++ b/phpgwapi/inc/class.groupdav_principals.inc.php
@@ -1223,6 +1223,8 @@ class groupdav_principals extends groupdav_handler
 		{
 			foreach((array)$add_proxys as $app)
 			{
+				if (!isset($GLOBALS['egw_info']['user']['apps'][$app])) continue;
+
 				switch($app)
 				{
 					case 'resources':