[Zope] ExtImage and PUT_factory: no success :-(

I want to use a PUT_factory to create ExtImages instead of plain Images via FTP. My external method PUT_factory looks like this: # from OFS.Image import Image from Products.ExtFile.ExtImage import ExtImage import string def PUT_factory(self, name, typ, body): '''create ExtImage instead of plain Image''' major, minor = string.split(typ, '/') if major == 'image': # return Image(name, '', '') return ExtImage(name, '', '') return None When I use the commented parts (plain Image) all is fine, with ExtImage I get '426 Error creating file.' TIA, Stefan -- Things work better when plugged in