I'm getting the same protocol error on Debian :~$ caffeine
INFO:root:caffeine is inhibiting desktop idleness Protocol error: bad 3 (Window); Sequence Number 11 Opcode (20, 0) = GetProperty Bad resource 0 (0x0) at -e line 15. INFO:root:caffeine is no longer inhibiting desktop idleness :~$ uname -a Linux #hostname 4.15.0-3-amd64 #1 SMP Debian 4.15.17-1 (2018-04-19) x86_64 GNU/Linux Desktop env: xfce4 Packagelist: https://pastebin.com/mEtQkU6P Screensaver: xscreensaver Packagelist :~$ apt search xscreensaver |grep installed xscreensaver/stable,testing,unstable,now 5.36-1 amd64 [installed] xscreensaver-data/stable,testing,unstable,now 5.36-1 amd64 [installed] -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1700419 Title: caffeine 2.9.4 isn't working on Ubuntu 16.04 To manage notifications about this bug go to: https://bugs.launchpad.net/caffeine/+bug/1700419/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs