Cannot disable Signup

Hello,

I’m using GitLab Community Edition 8.7.4 installed just today and have it running quite fine.
However, I would like to control who can use the service and so do not want users to be able to register for their own account.
Looking at the documentation, I should be able to go to the Admin area and untick “Sign up” under Features.
However, when I go there, all I see next to “Sign up” is a green dot and no way to untick anything.

I must be missing something obvious but I can’t figure out what it is.
Would you have any clue?

Regards

Well, once again, sorry for the noise, I finally found the checkbox.
For reference, it is here:

Admin Area
Settings, in the left menu

What I did not realize that it was at the bottom and that the menu is scrollable, independent from the main content.
Once in there, the checkbox is under the Sign-in Restrictions section.