Could you provide more details (code) about your issue? I was also wondering if you've tried using a custom plugin to bypass the problem, something like:

class IgnoreUnknownFieldsPlugin(MessagePlugin):
    def unmarshalled(self, context):
        # Remove unknown elements before SUDS processes them
        if hasattr(context.reply, 'children'):
            known_elements = [el for el in context.reply.children if el.name in context.reply.__metadata__.sxtype.rawchildren]
            context.reply.children = known_elements

client = Client(spec_path, plugins=[IgnoreUnknownFieldsPlugin()], faults=False)