[flexcoders] BitmapData Argument: Error #1063: Arg count mismatch on object util.copy

[method_air]

I'm creating a deep copy of an object which has a BitmapData property using 
ObjectUtil.copy and 'registerClassAlias', eg:

registerClassAlias("flash.display.BitmapData", BitmapData);

...but I'm getting the error: ArgumentError: Error #1063: Argument count 
mismatch on flash.display::BitmapData(). Expected 2, got 0

Is there a workaround?

Thanks,

Philip