pistons activate if observers are nearby but not connected

Put the summary of the bug you're having here

What I expected to happen was...:
that the piston does not activate with observers that are not connected

What actually happened was...:
the piston is activated with the observers without them being connected

Steps to Reproduce:
1. place observers making a clock
2.to two blocks place a piston (not connected to the observer)
3.The piston is activated with the observers after activating it for a second