Incorrect proxy class getting generated for WCF service

Question

I have a WCF service which as the followoing operation

OpResponse Op(OpRequest req);

Where OpResponse and OpRequest are Message Contracts.

When I try to generate a proxy for this class using Visual Studio 2008 Add Service Reference option.

It is generating a Proxy operation as

OpResponse Op(OpRequest1 req);

Instead of OpRequest it is creating a MessageContract named OpRequest1 and creates a DataContract named OpRequest and adds it as the child to the OpRequest1 Message Contract.

This behaviour only happes if I check "Always Generate Message Contracts" check box .

Otherwise OpRequest alone is getting generated as expected.

Any body came accross this issue?