Gelf logging with docker-compose

Question

I've googled the f out of this.

here is the log driver config for my docker container in the compose file

       driver: gelf
       options:
          gelf-address: "http://graylog:12201"

I created a GELF HTTP input in the admin console. I know that graylog is accessible at 12201, because if I ssh into a container and run

curl -X POST -H 'Content-Type: application/json' -d '{ "version": "1.1", "host": "example.org", "short_message": "A short message", "level": 5, "_some_info": "test" }' 'http://graylog:12201/gelf'

Then I can see the log message.

The problem is, it seems like I have to add the /gelf to the address, but docker complains if I try to do that. But no other curl commands work without it, and I can't seem to get it to work with TCP or UDP at all. So.... what am I doing wrong?