diff --git a/phpgwapi/inc/class.egw_session.inc.php b/phpgwapi/inc/class.egw_session.inc.php
index 18c1205c4b..4af1b7fd8b 100644
--- a/phpgwapi/inc/class.egw_session.inc.php
+++ b/phpgwapi/inc/class.egw_session.inc.php
@@ -1078,15 +1078,16 @@ class egw_session
 		}
 
 		// append the url to the webserver url, but avoid more then one slash between the parts of the url
-		if (($url[0] != '/' || $GLOBALS['egw_info']['server']['webserver_url'] != '/') && strpos($url, $GLOBALS['egw_info']['server']['webserver_url']) === false)
+		$webserver_url = $GLOBALS['egw_info']['server']['webserver_url'];
+		if (($url[0] != '/' || $webserver_url != '/') && (!$webserver_url || strpos($url, $webserver_url) === false))
 		{
-			if($url[0] != '/' && substr($GLOBALS['egw_info']['server']['webserver_url'],-1) != '/')
+			if($url[0] != '/' && substr($webserver_url,-1) != '/')
 			{
-				$url = $GLOBALS['egw_info']['server']['webserver_url'] .'/'. $url;
+				$url = $webserver_url .'/'. $url;
 			}
 			else
 			{
-				$url = $GLOBALS['egw_info']['server']['webserver_url'] . $url;
+				$url = $webserver_url . $url;
 			}
 		}