Cast loaded swf content to interface

Hi, I’m trying to load a external swf using the Loader object, and that part seems to be working fine. But, I can’t seem to be able to cast the LoaderInfo.content to a interface that it’s document class implements. This should be possible, shouldn’t it?

public function load()
    _urlRequest = new URLRequest("http://localhost/test.swf");

    _loader = new Loader();
    _loader.contentLoaderInfo.addEventListener(Event.INIT, onRequestComplete);
    _loader.load(_urlRequest, new LoaderContext(false, ApplicationDomain.currentDomain));

function onRequestComplete(event:Event):void
    var loaded:IMyInterface = IMyInterface(_loader.contentLoaderInfo.content);