Flex :: Have A Button Not Fire On Space Key If It Has Focus?

The behavior I'm trying to prevent is after a user clicks on a button, the button retains focus, and then if the user hits the space key, the button fires again. So I thought it could be solved either by setting the focus elsewhere, or by having the button ignore the space key. I've tried adding the following keyDown event listener on the button, but it didn't work.

private function btn_keyDown(event:KeyboardEvent):void {
// try to ignore spaces, i.e. don't click on SPACE when it has focus
if (event.keyCode == Keyboard.SPACE) {
}
}

I tried changing focus by doing the following, at the end of the function that's called when the button is clicked:

stage.focus = parent;