[Twisted-Python] FTP/VFS -- registerProducer error

Modeling my code off the FTP server example (http://twistedmatrix.com/trac/attachment/ticket/1579/ftp_server_example.py), I coded my own FTPRealm class to use an inmem vfs instead of the local filesystem. I can browse and download data from it without issue, but anytime I attempt to upload a file, I get this error: File "twisted/protocols/ftp.py", line 421, in registerConsumer self._cons.registerProducer(self, True) exceptions.AttributeError: _FileToConsumerAdapter instance has no attribute 'registerProducer' I'm setting up the avatar with the line: avatar = FileSystemToIFTPShellAdaptor(pathutils.FileSystem(inmem.FakeDirectory())) Full code is available here: http://rafb.net/p/FgTbiP80.html Any help would be greatly appreciated.