diff --git a/app/helpers/application_helper.rb b/app/helpers/application_helper.rb
index 1eabadcfc..479b2a293 100644
--- a/app/helpers/application_helper.rb
+++ b/app/helpers/application_helper.rb
@@ -606,7 +606,7 @@ module ApplicationHelper
       @calendar_headers_tags_included = true
       content_for :header_tags do
         javascript_include_tag('calendar/calendar') +
-        javascript_include_tag("calendar/lang/calendar-#{current_language}.js") +
+        javascript_include_tag("calendar/lang/calendar-#{current_language.to_s.downcase}.js") +
         javascript_include_tag('calendar/calendar-setup') +
         stylesheet_link_tag('calendar')
       end