bin/discourse-start setup fails: POSTGRES_PORT seems to be wrong

[stuartlangridge]

~/discourse-docker$ bin/discourse-start setup
+ exec sudo docker run -e REDIS_PROVIDER_URL=redis://user@100.85.250.86:49153 -e POSTGRES_HOST=100.85.250.86 -e POSTGRES_PORT=0.0.0.0:49155 -e POSTMARK_API_KEY= -e DISCOURSE_HOST=bvdiscourse.cloudapp.com -v /home/badvoltage/discourse-docker/data/discourse-public:/discourse/public srid/discourse setup
+ bundle exec rake db:create
invalid port number: "0.0.0.0:49155"

This seems to be being caused by this (code taken from bin/postgresql-info):

$ sudo docker ps | grep srid/postgresql:9.1 | awk '{print $1}'
299eb624837f
$ sudo docker port 299eb624837f 5432
0.0.0.0:49155

I think that the docker port command ought to be printing just a port number, not printing an IP and port number. I haven't changed any postgres configuration, and I followed the steps in the README. Do I need to tweak some configuration somewhere?