--- a/web/form.py	Fri Nov 27 09:10:40 2009 +0100
+++ b/web/form.py	Fri Nov 27 09:14:31 2009 +0100
@@ -42,16 +42,20 @@
     """abstract form mix-in
     XXX: you should inherit from this FIRST (obscure pb with super call)
     """
+    force_session_key = None
 
     def session_key(self):
         """return the key that may be used to store / retreive data about a
         previous post which failed because of a validation error
         """
-        return '%s#%s' % (self.req.url(), self.domid)
 
     def __init__(self, req, rset, **kwargs):
         super(FormMixIn, self).__init__(req, rset, **kwargs)
         self.restore_previous_post(self.session_key())
+        try:
+            return self.force_session_key
+        except AttributeError:
+            return '%s#%s' % (self.req.url(), self.domid)
 
     def restore_previous_post(self, sessionkey):
         # get validation session data which may have been previously set.