Optional fields added in WSDL. Does the Client need to be recompiled?

Can someone tell me if I need to recompile a webservice client when the WSDL changes such that new OPTIONAL fields are added? The server is deployed with new WSDL related skeletons but can the client run without any problems if it is still run based on the stubs generated from the older version of WSDL (which does not have those new optional fields)?

Thanks in advance.

What happens if the server supplies that options fields to the client ??