Clojurians Log v2

How do I expose an nREPL from inside Dokku? I'm deploying my Clojure app to an EC2 Ubuntu box via Dokku, and despite setting a proxy-port, I keep getting Long overflow when I try to connect, even locally from the machine. In my Dockerfile, I have exposed the nREPL port along with the web port:

...
EXPOSE 8080
EXPOSE 7889

The bind host is 0.0.0.0 and I can see the nREPL server started in the logs, but I can't connect to it. I tried setting the nginx proxy port like so:

dokku proxy:ports-add myapp http:7889:7889

I can only assume http is the wrong transport, but Dokku only supports http and https.