1136 error with a KeyboardEvent

[databell]

I'm trying to add a KeyBoard event in addition to the MouseEvent I already have for my function. So I set up the following code to handle that but it's giving me 1136 errors looking for an argument inside the parenthesis when in reality, it doesn't need one. What to do?

stage.addEventListener(KeyboardEvent.KEY_DOWN, onKeyPressed);

function onKeyPressed(evt:KeyboardEvent):void {
switch (evt.keyCode) {
case Keyboard.RIGHT:
slideRight();
break;
case Keyboard.LEFT:
slideLeft();
break;
}
}