Relative GitLab URL - Wrong Links in Jira Comments

I'm running Omnibus GitLab CE 8.8.1 on Debian 8 behind a reverse proxy at a relative URL:

https://public.my.domain/gitlab is proxied to http://gitlab.private.my.domain

That works fine, except for the generated comments in Jira. There, the URLs for the GitLab user and commit are generated as:

https://public.my.domain/gitlab/gitlab/u/jdoe

https://public.my.domain/gitlab/gitlab/group/project/commit/asdf

The problem is the doubled /gitlab. Changing the URL setting from url to base_url in jira_service.rb line 250 appears to fix it:

def resource_url(resource)
  "#{Settings.gitlab['base_url'].chomp("/")}#{resource}"
end