The Wither's health bar dosen't visually go down when it has the NoAI NBT tag

I don't know if this has already been reported (I did check) but in snapshot 15w31b, spawning a wither with no AI and hitting it with any weapon will damage it but its health bar will look as though it hasn't been hit. Note that it did go down before 1.9 snapshots.

How to reproduce:
1. Spawn a Wither with no AI
2. Hit it with a diamond sword a few times
3. Watch its health bar stay untouched