Custom Splash Potions Don't Work

Custom splash or custom lingering potions come out as splash water bottles.

To recreate:
/give @p splash_potion 1 0 {CustomPotionEffects:[

{Id:10,Amplifier:1,Duration:1200}

]}

This should give a Splash Potion of Regeneration, but instead it gives a splash bottle that does nothing when thrown.