Comment 177 for bug 518056

@Geraldo: When seeing your comment #175, I can't help thinking of bug #1573755. It's a subtle issue, and to check if that is what you have, you can either enter a guest session or create a new test user.

Otherwise, one observation I have made is that Wayland (enabled by default in Ubuntu 17.10, but won't be in Ubuntu 18.04) makes this more difficult. So logging in to Xorg sessions is safer so far in this respect.