Currently OFS.Folder.Folder doesn't have a constructor, so (I think) defaults to that of ExtensionClass.Base which accepts anything. The problem is that a number of places in the code, and a number of people, expect ob=Folder(id) to create a correct folder, whereas the id is actually not used. Noa got bitten by this today, and a number of tests even call Folder with an argument. Whereas the rest of the code painstakingly does ob = Folder() ob.id = id Is anyone opposed to having a def __init__(id=None, title=None): if id is not None: self.id = id if title is not None: self.title = title in Folder ? Florent -- Florent Guillaume, Nuxeo (Paris, France) +33 1 40 33 79 87 http://nuxeo.com mailto:fg@nuxeo.com