Using headbutt on the party menu doesn't work

[yonicstudios]

For some odd reason, using headbutt via the party menu on the events I used for headbutt will not work, even if I had renamed the events to HeadbuttTree. It keeps saying "Can't use that here."

My guess was that I should've used another way of firing up the HeadbuttTree event, but that didn't seem to work on "Collide" nor "Event Collide".

The scripts don't seem to be wrong, either...

HiddenMoveHandlers::CanUseMove.add(:HEADBUTT,proc{|move,pkmn|
   facingEvent=$game_player.pbFacingEvent
   if !facingEvent || facingEvent.name!="HeadbuttTree"
     Kernel.pbMessage(_INTL("Can't use that here."))
     return false
   end
   return true
})

It does work when you use it outside the party menu, though. What could this mean?