diff --git a/api/js/login.js b/api/js/login.js
index b2af0133b9..32d1069fea 100644
--- a/api/js/login.js
+++ b/api/js/login.js
@@ -16,7 +16,7 @@ egw_LAB.wait(function()
 	jQuery(document).ready(function()
 	{
 		// lock the device orientation in portrait view
-		if (screen.orientation) screen.orientation.lock('portrait');
+		if (screen.orientation && typeof screen.orientation.lock == 'function') screen.orientation.lock('portrait');
 
 		function do_social(_data)
 		{