system.defaults.screensaver.askForPasswordDelay not working

[rmgpinto]

I've set system.defaults.screensaver.askForPasswordDelay = 0;
but when I set my laptop to sleep, and move the mouse after a couple of seconds, it doesn't ask for my password.

The setting: Lock Screen -> Require password after screen saver begins or display is turned off is still at 5 minutes instead of immediately.