I would really like to be able to pass custom exceptions over the wire in PB. Previous discussion on this list ended with the conclusion that it currently isn't possible without hacking a local copy of Twisted. I have done that to get the result I want, with minimal testing, and would like to get some discussion going around this topic. Attached are 3 test files, s.py for the server, c.py for the client, and e.py for the error definitions which are imported by both s.py and c.py. If I make the following modification to my local copy of twisted/spread/pb.py in the CopyableFailure's getStateToCopy method, the custom error is passed back as I want. #state['value'] = str(self.value) # Exception instance state['value'] = self.value # Exception instance I was wondering if there is a reason we wouldn't want to change the code to check for registered unjellyables for the exception, and return them (or rather go through the jelly/unjelly process) if they exist, but return the string representation otherwise. Maybe that is more complicated than I realize. Any thoughts or suggestions on how we might make this possible? Thanks. -Justin