Happy Ghast becomes fully black when one block is above it

Expected behavior

The happy ghast doesn’t turn into a solid black colour.

Steps to reproduce

• Grow happy ghast

• Put harness on happy ghast

• Ride happy ghast and park it on the floor

• Put blocks on top of happy ghast until the mob turns black (/setblock ~ ~ ~ stone)

• Remove remaining blocks to make it look weirder I guess.

This tends to happen only at the center of the happy ghast.