piston wont get back when lever is off!!

Put the summary of the bug you're having here

*I tried some piston stuff, so i flickered a lever to on so my piston pushed, then i turned it off and piston was still pushing!
piston should stop pushing

*piston should stop pushing
piston didnt stop pushing

Steps to Reproduce:
1. make a little "l" with blocks like this: L <--- put a redstone on that block and lever at the 2nd block and a piston underneath
2. drag the lever, and the piston pushes and then turn the lever off, and it will still push!
3. ...