Summoned Zombie/Skeleton horses don't have their armor

What's the exact command you've used ?

It's on the "HorseCommand" screen:
/summon EntityHorse ~ ~ ~ {Type:4,Saddle:1,ArmorItem:{id:419}}.

I've tried a lot more commands (other horse types, with or without saddle, etc...) and still same result.

Confirmed for 14w21b
for Zombie and Skeleton Horse

Possible reason:
It seems like the skeleton and zombie horse don't have armor slots

*Added screenshot

confirmed, but porbobly won´t fix as the zombie and skeleton variants are not supported mobs, you shouldn´t say horse in the title but zombie and skeleton horse

Skeleton / Zombie horses are not supported yet.

Now with Skeleton Traps this Bug report should get Reopened at least for Skeleton Horses
Can confirm for 15w49b

They don't have an inventory slot for horse armor. Still invalid.