diff --git a/ckan/config/middleware.py b/ckan/config/middleware.py
index bdf1ff016a0..4df0aa84cb0 100644
--- a/ckan/config/middleware.py
+++ b/ckan/config/middleware.py
@@ -338,8 +338,8 @@ def __call__(self, environ, start_response):
             key = ''.join([
                 environ['HTTP_USER_AGENT'],
                 environ['REMOTE_ADDR'],
-                environ['HTTP_ACCEPT_LANGUAGE'],
-                environ['HTTP_ACCEPT_ENCODING'],
+                environ.get('HTTP_ACCEPT_LANGUAGE', ''),
+                environ.get('HTTP_ACCEPT_ENCODING', ''),
             ])
             key = hashlib.md5(key).hexdigest()
             # store key/data here