Zombie sleeping

What I expected to happen was...:
I'm expecting to the zombie fall down and disappear

What actually happened was...:
The zombie fall down, but it didn't disappear

Steps to Reproduce:
1. Try to kill a (baby) zombie with an iron golem or a sword
2. Depending on your choice, you'll know the results, but with some surprise (maybe if you're lucky)
3. After all of this, the zombie will look like it's sleeping 😴🛌

Obs: The zombie will eventually disappear when you move away from it