Stage.align parameters aren't working?

programming flash
1

Hi all, im using this code:

Stage.align = "BR";
var stageListener: Object = new Object();
stageListener.onResize = positionContent;
Stage.addListener(stageListener);
function positionContent():Void {
  mcLogo._x = Stage.width - mcLogo._width;
  mcLogo._y = Stage.height - mcLogo._height;
}
positionContent();

…to fix the position of my MC, but the parameter “BR” (and all others) aren’t effecting.
My mc always shows up in the bottom right corner.

any help?