diff -r 80ee6397c087 -r 67a86c70e42e entity.py
--- a/entity.py	Thu Apr 30 13:06:10 2009 +0200
+++ b/entity.py	Thu Apr 30 13:06:44 2009 +0200
@@ -127,6 +127,7 @@
                     if wdgname == 'StringWidget':
                         wdgname = 'TextInput'
                     widget = getattr(formwidgets, wdgname)
+                    assert hasattr(widget, 'render')
                     AutomaticEntityForm.rwidgets.tag_relation(
                         widget, (etype, rtype, '*'), 'subject')
         return super(_metaentity, mcs).__new__(mcs, name, bases, classdict)