Degrade sur text dynamique ne marche pas quand le texte change...?

var container:MovieClip = new MovieClip();
addChild(container);

var txt:TextField = new TextField();
txt.text = "test";

container.addChild(txt);

var my_fmt:TextFormat = new TextFormat();
my_fmt.font = "Arial";
my_fmt.size = 50;
txt.setTextFormat(my_fmt);
txt.embedFonts = true;

masqueTitre.mask = container;

function testClick(evt:MouseEvent){
	txt.text = "TEST1";
	}
test.addEventListener(MouseEvent.CLICK, testClick);
test.buttonMode = true;