When using entitydata or replaceitem on non-humanoid type mobs (pigs, creepers, etc) equipment doesn't render.

As you can see in the picture the pig has an ender chest on it's head. However, it isn't being displayed. (Note the ender chest was equiped using the replaceitem command). The same thing happens when trying to equip a leather helmet using the entitydata command. It shows up in the data tag, but it doesn't render.

These commands work fine on myself and other humanoid mobs (zombies, skeletons).

To Duplicate:
/summon Pig ~ ~ ~

{NoAI:1}

/replaceitem entity @e[type=Pig] slot.armor.head ender_chest

/entitydata @e[type=Pig] {Equipment:[0:{},{},{},{},

{id:"minecraft:leather_helmet"}

]}