--- a/web/http_headers.py	Tue Sep 23 17:34:36 2014 +0200
+++ b/web/http_headers.py	Thu Sep 25 15:49:13 2014 +0200
@@ -1567,7 +1567,7 @@
     'Server': (unique, str, singleHeader),
     'Set-Cookie': (generateSetCookie,),
     'Set-Cookie2': (generateSetCookie2,),
-    'Vary': (generateList, singleHeader),
+    'Vary': (set, generateList, singleHeader),
     'WWW-Authenticate': (generateWWWAuthenticate,)
 }