"Access denied" when trying to clone a wiki via HTTPS

This issue seems somewhat related to !7832 (merged) , #24931 (closed) etc.

When trying to clone a wiki git repo via HTTPS, I receive a remote: Access denied.

remote: Access denied
fatal: unable to access 'https://something.githost.io/project/meta.wiki.git/': The requested URL returned error: 403

Cloning via ssh works fine. After enabling the "Repository" feature for the projekt, cloning by HTTPS works, too.