diff --git a/modules/luci-base/ucode/dispatcher.uc b/modules/luci-base/ucode/dispatcher.uc
index 50c1a7d0f2..1d10d7876d 100644
--- a/modules/luci-base/ucode/dispatcher.uc
+++ b/modules/luci-base/ucode/dispatcher.uc
@@ -103,6 +103,8 @@ function determine_request_language() {
 
 	if (lang == 'auto')
 		lang = 'en';
+	else
+		lang = replace(lang, '_', '-');
 
 	if (load_catalog(lang, '/usr/lib/lua/luci/i18n'))
 		change_catalog(lang);