Error: Splash and Lingering Regen Potions Not Damaging Undead Mobs

Error: Splash and Lingering Regeneration Potions Not Damaging Undead Mobs

I played In 1.8.9 and I play creative mode for fun a lot and use regeneration on undead mobs (zombies,skeletons, etc) then the snapshot does not do this is it a bug or a change?

1. /summon Skeleton ~ ~ ~
2. Use a regeneration potion to throw at it and no effect (16w03a)
3. Instant Health still effects though