When I placed an upward-facing sticky piston at y=1 and powered it, the sticky piston pushed the block but when I de-powered it, it did not retract.

What I expected to happen was...:
the sticky piston would retract and pull the block back with it

What actually happened was...: 

the block was left behind 

Steps to Reproduce:

1. Dig down to y=1
2. Place a sticky piston facing upwards and then a block on top of it
3. Power the sticky piston and when you retract it the block will stay behind