How to nest the path of the entry point?

Hi there, up until now I have been testing crossbar on a local server but now I am trying to get it to work under a proxy. The proxy must impose a base directory on the url so now my ws server is nested. Basically my question is how I configure ‘path’ so that it recognizes a directory that is two deep? Something like this:

wss://127.0.0.1:9000/proxyroot/ws

I have tried to make path into ‘proxyroot/ws’ but crossbar complains about that. Please help, thanks.