"Invulnerable:1" Not Working

Just trying to make a map, until I tried to /summon a pig with Unvulnerable:1. Didn't work.

I killed him using this *EXACT* code: /summon Pig ~ ~1 ~ {Invulnerable:1}

Also tried this code: /summon Pig ~ ~1 ~ {NoAI:1,Invulnerable:1}

Both don't work.