[Zope] XMLRPC and Allow_None

Hi, I am getting this error: cannot marshal None unless allow_none is enabled I now it is because I am passing a Null value is there a way to allow this by just disregarding the function? This is what my client code looks like: def dirInfo(userName): server = xmlrpclib.Server("http://localhost:8080/RPC2") user = server.sample.dirInfo(userName) return user So it passes a userName but if the user name is null it needs to be able to disregard the request. Any suggestions? Thanks, Laura