Predicting the external SWF content

Hi,
I am importing an SWF as library at runtime

  private function loadDeck(str:String)
  {
   var ldr:Loader = new Loader();
   var request:URLRequest = new URLRequest(str);
   var ldrContext:LoaderContext = new LoaderContext(false, ApplicationDomain.currentDomain); 
   ldr.load(request, ldrContext);
   ldr.contentLoaderInfo.addEventListener(Event.COMPLETE, deckLoaded, false, 0, true);
  }
  function deckLoaded(e:Event):void
  {
   trace("DECK LOADED");
  }

Then I can access all SWF linkages directly, as I added the SWF library to the app-domain.
But…! When I instantiate a new object from the SWF library, the compiler does not know the new Class, and tells me it is not a known object, obviously.

I fixed this problem deselecting “Strict Mode” from the FLA publish settings, but which is the best way to declare the exhistance of a certain class of an external SWF before it is loaded?