HTTP Clone URL wrong

I recently set up gitlab with nginx, which is only reachable locally, and apache as a proxy, so I can reach gitlab from outside. I can’t create subdomains so this is the way it has to be. Everything runs fine, except the HTTP clone URL has the host of my local nginx server in it, which apparently does not work outside the server. I could change the host for the ssh clone url in the gitlab.rb but I can’t seem to find a way to change the host for the http url.
So my simple question is, how do I do this?

Thanks for your help