--- a/cubicweb/req.py	Thu Nov 17 10:47:52 2016 +0100
+++ b/cubicweb/req.py	Thu Nov 17 10:53:04 2016 +0100
@@ -74,6 +74,7 @@
         # should be emptied on commit/rollback of the server session / web
         # connection
         self.user = None
+        self.lang = None
         self.local_perm_cache = {}
         self._ = text_type