--- a/web/form.py	Wed Sep 16 11:28:07 2015 +0200
+++ b/web/form.py	Wed Sep 16 13:57:21 2015 +0200
@@ -20,6 +20,8 @@
 
 from warnings import warn
 
+from six import add_metaclass
+
 from logilab.common.decorators import iclassmethod
 from logilab.common.deprecation import deprecated
 
@@ -74,8 +76,8 @@
     found
     """
 
+@add_metaclass(metafieldsform)
 class Form(AppObject):
-    __metaclass__ = metafieldsform
     __registry__ = 'forms'
 
     parent_form = None