diff --git a/ddportfolioservice/lib/base.py b/ddportfolioservice/lib/base.py
index 4a93095..43edcae 100644
--- a/ddportfolioservice/lib/base.py
+++ b/ddportfolioservice/lib/base.py
@@ -40,7 +40,7 @@ class BaseController(WSGIController):
         # set language environment
         for lang in request.languages:
             try:
-                add_fallback(lang)
+                add_fallback(lang.replace('-', '_'))
             except:
                 pass
         c.messages = {'errors': [], 'messages': []}