diff --git a/phpgwapi/inc/class.sessions.inc.php b/phpgwapi/inc/class.sessions.inc.php
index 9328a44706..d16de0e7ec 100644
--- a/phpgwapi/inc/class.sessions.inc.php
+++ b/phpgwapi/inc/class.sessions.inc.php
@@ -1326,6 +1326,13 @@
 		*/
 		function new_session_id()
 		{
+			# when synchronizing using syncml, we already have php4 based session started
+			# and we are currently not allowed to change the sessionid later
+			# to solve this problem, we simply return the current session_id
+			if(basename($_SERVER["REQUEST_URI"]) == 'rpc.php' && session_id() != '') {
+				return session_id();
+			}
+			
 			return md5($GLOBALS['egw']->common->randomstring(15));
 		}