Login broken on Firefox with LastPass

Logging in to GitLab using Firefox with the LastPass extension (https://addons.mozilla.org/da/firefox/addon/lastpass-password-manager/) installed gets the user redirected to /users/undefined, which gives a 404 error. However, after manually navigating to /, everything works just fine.

The same thing happened to me when clicking the confirmation link after creating my GitLab.com account.

This was reported as issue #10110 (closed) on GitHub: https://github.com/gitlabhq/gitlabhq/issues/10110

Still happening for me with GitLab 8.9.3 and Firefox 47.0.1.