Rails drop when pushed up by piston

Working:
1. Block in the air
2. Rail on it
3. Piston facing down above
4. Activate: Rail doesn't drop, gets pushed down with block

Not working:
1. Block in the air
2. Rail on it
3. Piston facing up under the block
4. Activate: Instead of doing the exact opposite (pushing block and rail up), it pushes the block up and the rail drops.