ActionScript :: Toggling Boolean - Always Tracing True For Mouse Click

This code is written in simple ActionScript, but I'm assuming this problem of mine would occur in all languages that have boolean datatypes. I'm simply clicking the stage so that my boolean variable reverses its value and than traces/prints/logs it's new value. However, it's always tracing true instead of switching between true and false for each mouse click.

var myBool:Boolean;
stage.addEventListener(MouseEvent.CLICK, mouseClickHandler);
function mouseClickHandler(evt:MouseEvent):void {
changeBoolean(myBool);
} function changeBoolean(boolean:Boolean):void {
boolean = !boolean;
trace(boolean);
}