Error 502 when enabled Gitlab Docker Registry at GitLab 8.8

I installed gitlab 8.8 from packages on ubuntu 16.04 following this manual. https://about.gitlab.com/downloads/#ubuntu1604

When I add line

registry_external_url 'https://gitlab.example.com:4567'

to my /etc/gitlab/gitlab.rb and reconfiguring gitlab I seen this error:

Error 502 Bad Gateway.

Try to delete this line and all fine. How can I setup Gitlab docker registry properly?