The xmlrpclib library represents a Fault object with an extraneous 'args' member field. The reason for this is that the dump function blindly marshals all variables of the Fault object, and since Fault is a subclass of Exception it inherits the 'args' attribute. According to the XML-RPC spec, adding additional fields to a Fault response is not allowed. The attached patch is a simple solution to the problem. Sample Fault XML output that shows the problem: faultCode 900 args faultString boo