CredentialsManagementTool.register tries to send a function thru PB

Peer will receive following PB traceback:
Traceback (most recent call last):
  File "c:\python27\lib\site-packages\twisted\spread\banana.py", line 153, in gotItem
    self.callExpressionReceived(item)
  File "c:\python27\lib\site-packages\twisted\spread\banana.py", line 116, in callExpressionReceived
    self.expressionReceived(obj)
  File "c:\python27\lib\site-packages\twisted\spread\pb.py", line 514, in expressionReceived
    method(*sexp[1:])
  File "c:\python27\lib\site-packages\twisted\spread\pb.py", line 826, in proto_message
    self._recvMessage(self.localObjectForID, requestID, objectID, message, answerRequired, netArgs, netKw)
--- <exception caught here> ---
  File "c:\python27\lib\site-packages\twisted\spread\pb.py", line 840, in _recvMessage
    netResult = object.remoteMessageReceived(self, message, netArgs, netKw)
  File "c:\python27\lib\site-packages\twisted\spread\flavors.py", line 109, in remoteMessageReceived
    kw = broker.unserialize(kw)
  File "c:\python27\lib\site-packages\twisted\spread\pb.py", line 776, in unserialize
    return unjelly(sexp, self.security, None, self)
  File "c:\python27\lib\site-packages\twisted\spread\jelly.py", line 1136, in unjelly
    return _Unjellier(taster, persistentLoad, invoker).unjellyFull(sexp)
  File "c:\python27\lib\site-packages\twisted\spread\jelly.py", line 632, in unjellyFull
    o = self.unjelly(obj)
  File "c:\python27\lib\site-packages\twisted\spread\jelly.py", line 669, in unjelly
    ret = thunk(obj[1:])
  File "c:\python27\lib\site-packages\twisted\spread\jelly.py", line 848, in _unjelly_dictionary
    self.unjellyInto(kvd, 1, v)
  File "c:\python27\lib\site-packages\twisted\spread\jelly.py", line 747, in unjellyInto
    o = self.unjelly(jel)
  File "c:\python27\lib\site-packages\twisted\spread\jelly.py", line 643, in unjelly
    raise InsecureJelly(jelType)
twisted.spread.jelly.InsecureJelly: function