Clojurians Log v2

I've tried adding

:figwheel {:server-port 5309}

to the top level of my project.clj and

:figwheel {:websocket-url ""}

in the build map. When I connect to localhost:5309 in my browser, the js is loaded correctly. But the developer console spams

WebSocket connection to '' failed: 

It's like the :websocket-url option is ignored 😕