GitLab Omnibus 8.8.4 - WebUI timeout after changing ngnix port - no errors in logs

I’ve installed GitLab with Omnibus package on a CentOS 6.4. After setting the external_url in /etc/gitlab/gitlab.rb and executing gitlab-ctl reconfigure I was able to access the setup page at http://my.ip.here/ without problems.

But, after changing the external_url again to http://my.ip.here:23080, I cannot access the login page, be it through http://my.ip.here:23080/ or http://my.ip.here/; The page just timeouts. Reverting the external_url back makes everything work again on port 80.

netstat shows ngnix is listening in 23080 and in fact telnet will connect to it. But no response is ever sent. Tailing the logs during the requests with gitlab-ctl tail shows nothing.

What is the correct procedure to change the nginx port? What else needs to changed for GitLab to works in a non-standard port? How could I debug my issue?

Thanks in advance.