diff --git a/doc/gitlab-mattermost/README.md b/doc/gitlab-mattermost/README.md
index 96493b06368885a45ed4d6235eac7d4bf7c4ba68..e8746aa9d519888953d8a8ebdd36872994c6c941 100644
--- a/doc/gitlab-mattermost/README.md
+++ b/doc/gitlab-mattermost/README.md
@@ -61,6 +61,11 @@ gitlab_rails['enable'] = false
 
 where `Secret` and `Id` are `application secret` and `application id` received when creating new `Application` authorization in GitLab admin section.
 
+To enable integrations with GitLab, add the following on the GitLab Server:
+```ruby
+gitlab_rails['mattermost_host'] = "https://mattermost.example.com"
+```
+
 Optionally, you can set `mattermost['email_enable_sign_up_with_email'] = false` to force all users to sign-up with GitLab only. See Mattermost [documentation on GitLab SSO](https://docs.mattermost.com/deployment/sso-gitlab.html).
 
 ## Manually (re)authorising GitLab Mattermost with GitLab