What is wrong with this code?

1

Hi all, this is my code:


var request:URLRequest=new URLRequest("firstsound.mp3");
var snd1:Sound=new Sound();
snd1.load(request);
var song:SoundChannel=snd1.play();
song.addEventListener(Event.SOUND_COMPLETE, onPlaybackComplete);

function onPlaybackComplete(event:Event)
{
      bttn_snd2.visible = true;
      bttn_snd3.visible = true;
}

I get the following error output when I execute this code:

TypeError: Error #2007: Parameter listener must be non-null.
at flash.events::EventDispatcher/addEventListener() at MethodInfo-218()

Please help, the AS3 manual is not very helpfull

Thanks,

Louis