Piston wont power halfslab+redstone

Put the summary of the bug you're having here

What I expected to happen was...:
Both piston will power

What actually happened was...:
one piston powered

Steps to Reproduce:
1. Place a dubble slab and a high block half slab next to each other
2. Place redstone on them
3. Place the pistons how they supposed to power both
4. Put a lever on the dubble slab
5. Power and look [screenshots will help] I couldn't find something like this so i think i found a bug