Armor on Giant is rendering darker when Giant is holding an item

When a Giant isn't holding any item, its armor renders normally, however if it is holding an item it renders darker.

Note: The commands are for 15w31a+

Giant with no item

/summon Giant ~ ~ ~ {ArmorItems:[{},{},{},{id:diamond_helmet}]}

Giant with item

/summon Giant ~ ~ ~ {ArmorItems:[{},{},{},{id:diamond_helmet}],HandItems:[{id:stick}]}