Add Service to FileTransferVirtualThing

I have a VIrtualThing with a remote service defined and working perfectly. I would now like to add support for file transfer to this VirtualThing and so changed it to extend FileTransferVirtualThing instead of VirtualThing. I am able to compile and run but the initializeFromAnnotations() fails with an exception: 

ERROR c.t.c.client.things.VirtualThing - Service already defined: <remote service name>

I had to add exception handling around thing creating when I changed base classes. Is it possible you can't add remote services to a FileTransferVirtualThing?

Thanks for any insights or ideas on how to debug this!

Pat