Global hotkeys do not work with "media" and "pause" key

I tried to assign Super+P to !Play/Pause global hotkey. I use Xubuntu Linux 13.10. The Super key is also known as Win key - it is the key with Windows logo. I assigned it in settings, it appeared as Media+P. I restarted VLC. From that moment, P key alone worked as !Play/Pause (which prevented me to even write letter P in all other apps) and Super+P did nothing. I tried Alt+P and it worked as expected. I tried Pause (also known as !Pause/Break) key, because I don't use it at all and it would suit to the !Play/Pause needs by it's name. Also, it's single key, which is better than combination. However, only Unset appeared in settings and nothing worked as expected after restart.