--- a/web/http_headers.py	Thu Feb 14 15:38:25 2013 +0100
+++ b/web/http_headers.py	Thu Feb 14 16:01:24 2013 +0100
@@ -27,7 +27,7 @@
 
 def casemappingify(d):
     global header_case_mapping
-    newd = dict([(key.lower(),key) for key in d.keys()])
+    newd = dict([(key.lower(),key) for key in d])
     header_case_mapping.update(newd)
 
 def lowerify(d):