Armor Attribute not working?

I'm trying to make some armor with additional protection, making a leather armor chestplate act as something tougher for example. My test config grants the additional hearts, but not the armor.

TestChest:
Id: 299
Display: 'TestChest'
Options:
Color: 71,67,58
Unbreakable: true
HideFlags: true
Attributes:
Chest:
Armor: 4
Health: 20

Edit: the formatting did not carry over but that's not an issue. Formatted code found...

Armor Attribute not working?