Pistons facing up don't retract when pushing a redstone block

When a sticky piston or a regular piston pushing a redstone block and facing up stops receiving power, it won't retract. I discovered this while making a piston elevator that pushes a redstone block to the top.

What I expected to happen was...:
The facing up piston retracts when it stops receiving power.

What actually happened was...:
The facing up piston doesn't retract it stops receiving power. It only retracts when the redstone block is destroyed.

Steps to Reproduce:
1. Place a sticky piston or a regular piston facing up and place a redstone block on top.
2. Power the piston.
3. Unpower the piston.