diff --git a/lib/public/iservercontainer.php b/lib/public/iservercontainer.php
index 9c39ac7ae73..f8fa929239c 100644
--- a/lib/public/iservercontainer.php
+++ b/lib/public/iservercontainer.php
@@ -145,9 +145,10 @@ interface IServerContainer {
 	/**
 	 * get an L10N instance
 	 * @param string $app appid
+	 * @param string $lang
 	 * @return \OCP\IL10N
 	 */
-	function getL10N($app);
+	function getL10N($app, $lang = null);
 
 	/**
 	 * Returns the URL generator