--- a/web/http_headers.py	Mon Jul 28 17:22:49 2014 +0200
+++ b/web/http_headers.py	Tue Jul 29 16:26:09 2014 +0200
@@ -1561,7 +1561,7 @@
     'Server': (unique, str, singleHeader),
     'Set-Cookie': (generateSetCookie,),
     'Set-Cookie2': (generateSetCookie2,),
-    'Vary': (generateList, singleHeader),
+    'Vary': (set, generateList, singleHeader),
     'WWW-Authenticate': (generateWWWAuthenticate,)
 }