Another finding: starting gnome-session with `--builtin` instead of `--systemd` works around the problem.
- Bug#1040920: gnome-flashback: Gnome flashback un... Nikolaus Rath
- Bug#1040920: Acknowledgement (gnome-flashback: G... Nikolaus Rath
- Bug#1040920: Acknowledgement (gnome-flashbac... Alberts Muktupāvels
- Bug#1040920: Acknowledgement (gnome-flas... Nikolaus Rath
- Bug#1040920: Acknowledgement (gnome-flashback: G... Nikolaus Rath
- Bug#1040920: Acknowledgement (gnome-flashbac... Alberts Muktupāvels
- Bug#1040920: Acknowledgement (gnome-flas... Nikolaus Rath
- Bug#1040920: Acknowledgement (gnome-... Alberts Muktupāvels
- Bug#1040920: Acknowledgement (g... Nikolaus Rath
- Bug#1040920: Acknowledgemen... Alberts Muktupāvels
- Bug#1040920: Info received (Bug#1040920: Acknowledgem... Nikolaus Rath