diff --git a/kitsune/sumo/middleware.py b/kitsune/sumo/middleware.py
index dff47f768bf..5892671958d 100644
--- a/kitsune/sumo/middleware.py
+++ b/kitsune/sumo/middleware.py
@@ -34,9 +34,10 @@ def process_request(self, request):
         set_url_prefixer(prefixer)
         full_path = prefixer.fix(prefixer.shortened_path)
 
-        if 'lang' in request.GET:
+        if request.GET.get('lang', '') in settings.SUMO_LANGUAGES:
             # Blank out the locale so that we can set a new one. Remove lang
             # from the query params so we don't have an infinite loop.
+
             prefixer.locale = ''
             new_path = prefixer.fix(prefixer.shortened_path)
             query = dict((smart_str(k), v) for