Mobs specified to drop items doesn't do it. (Custom Mob drops)

So I'm trying to summon a Ghast riding a silverfish. And when the Ghast dies, there's supposed to be a 100% chance for an Iron Chestplate to drop and a 20% chance for an Diamond Axe to drop. However, none of them does. Eventhough I set one of the items to have a 100% drop chance. doMobLoot is true.

This does however work in 1.8.8. Which makes belive this is a bug.

Here's the command:

/summon Ghast ~ ~1 ~ {DropChances:[0.2f,0f,0f,1f,0f],Equipment:[{id:"diamond_axe",damage:0,Count:1},{},{},{id:"iron_chestplate",damage:0,Count:1},{}],Riding:{id:"Silverfish"}}