Custom mob loot Damage value still not working

/summon Zombie ~ ~2 ~ {Equipment:[{},{},{},{},{id:minecraft:leather_helmet,Count:1,Damage:54}],DropChances:[0.0f,0.0f,0.0f,0.0f,1.0f]}

will always no matter what the Damage value is drop an item with 25 durability left.