How to return a response with custom headers in Mux.jl?

Has anyone been able to get this working? I can do it with HttpServer, but I can’t figure out how to return them in Mux. For example

@app test = (
    Mux.defaults,
    page("/test", req -> Dict("body"=>"meh")),
    Mux.notfound()
)

returns an default response with no body no matter what the Dict is set to. I think the problem might be here but I’m having a hard time following the code.

@blairn provided a solution here.