diff --git a/lib/l10n.php b/lib/l10n.php
index ca53b3cf65..ee87900926 100644
--- a/lib/l10n.php
+++ b/lib/l10n.php
@@ -287,7 +287,7 @@ class OC_L10N{
 		}
 
 		if(isset($_SERVER['HTTP_ACCEPT_LANGUAGE'])) {
-			$accepted_languages = preg_split('/,\s*/', $_SERVER['HTTP_ACCEPT_LANGUAGE']);
+			$accepted_languages = preg_split('/,\s*/', strtolower($_SERVER['HTTP_ACCEPT_LANGUAGE']));
 			if(is_array($app)) {
 				$available = $app;
 			}