Creating Wither in 13w04a create some ghost block

What I expect to happen : Wither spawn normally like in 1.4.7

What actually happen : When the player create a Wither, only the Wither Skeleton Skull and the Soul Sand below it is completely gone. The other become a ghost block (can't created into another Wither, when destroyed in survival it take the same time as the normal block but doesn't drop anything).

How to trigger :
1. Create the Wither
2. Done

*Happen in creative too