Errors BitmapAsset & ByteArrayAsset missing Flex 4.9

[Federico Jakimowicz]

Hi! I'm building a "hello world" project using Starling and Feathers. When 
using sdk version Apache Flex 4.9 FP11.1 I get the following errors: 1017: The 
definition of base class BitmapAsset was not found.1017: The definition of base 
class ByteArrayAsset was not found. However this errors don't appear using sdk 
version Apache Flex 4.8.Any ideas what might be going on? kind regards