De-powering sticky pistons (that pull other sticky pistons) vanishes the pulled ones

In a circuit I was making, I was using several sticky pistons pushing&pulling others, in an ascending tower... Then, I downloaded and ran snapshot 13w09c and I found a bug that didn't show off in snapshot 13w09b. A sticky piston pulling another sticky piston makes the 2nd one (the sticky piston being pulled) vanish.