Upon creating the wither, It leaves ghost blocks

I tried to summon a wither and the blocks were left behind. Confirmed to work on easy difficulty and up.

What I expected to happen was...:
The wither would spawn and the soul sand blocks would disappear.

What actually happened was...:
The wither spawned and left the blocks behind.

Steps to Reproduce:
1. Summon a wither
2. Blocks will stay until right-clicked or until you re-enter the world