llPassTouches() problems

Is there a trick to using this function that I'm not aware of, or does it just not work?

I have two linked objects, one is a door "lock" and the other is a button that opens the (not linked) doors.

The idea is that whenever someone clicks on the door button, llMessageLinked() and link_message() are used to query the lock status from the child object that represents the "lock."

The lock is separate for two reasons: 1) It has a red/green light texture to indicate the lock status, and 2) When I (the owner) touch the lock object, I want it to lock/unlock the doors.

As it is now, when I touch the lock object, the touch is passed on to the root object (the button) and the doors open/close.

I'm calling llPassTouches(FALSE) in the state_entry() event of the lock object, but apparently to no effect. I've also tried doing this in state_entry() of the button, and it doesn't work there, either.

So, back to the original question: Is it broken, or is there just some trick that's not in the documentation?

I found the catch, I think.

I originally put llPassTouches(FALSE) in the child object to make sure it worked as expected, before I created any touch events in that object.

Apparantly, llPassTouches(FALSE) only works if the child object actually has a touch-related event handler.

As soon as I put in an empty touch-related event handler (on a testing whim), it quit passing the touch on to the parent.