Hello, z3c.form.datamanager.DictionaryField is a data manager which is registered for fields on a dict. In its __init__ it checks whether the data object is an instance of dict. So this data manager does neither work for UserDict nor PersistentDict/PersistentMapping. I'd like to change this but there are two possibilities and I'm not sure which is the best one: 1.) Add a subclasses of DictionaryField which is registered for UserDict and which checks whether the data object is an instance of UserDict. (PersistentDict and PersistentMapping are subclasses of UserDict.) 2.) Register DictionaryField for zope.interface.common.mapping.IMapping. This might have a problem as neither UserDict nor PersistentDict/PersistentMapping seem to provide this interface. (Why?) Any suggestions? Yours sincerely, -- Michael Howitz · mh@gocept.com · software developer gocept gmbh & co. kg · forsterstraße 29 · 06112 halle (saale) · germany http://gocept.com · tel +49 345 1229889 8 · fax +49 345 1229889 1 Zope and Plone consulting and development