Creeper hissing sound continues after it's dead

The hissing sound a creeper makes when it's about to explode continues even after you kill it.

What I expected to happen was...:
As soon as I kill the creeper, the sound should stop so I can tell whether I'm safe or not.

What actually happened was...:
The sound just keeps playing so you can't really be sure if you've killed all the creepers around you.

Steps to Reproduce:
Approach a creeper, let it start to charge its explosion and kill it before it blows up.