Screensaver Preferences: can't change idle time with keyboard

1. open Settings/Screensaver
2. type in new value into "Regard the computer as idle after:" (minutes) field
3. click on close
4. open Settings/Screensaver again
5. there is still the old value

The only way how to actually change the value is to use "+/-" next to the field at hand. It can be used in conjunction with entering the new value, but is not very straightforward. There should be a way how to enter the value directly.

xfce4-screensaver-0.1.10