squeaking noise from the rear coilovers how to fix

[Makis]

I changed the springs to my rear coilovers and I am getting some squeaking noise that is consistent with the car movement up/down. It comes from both sides and it appear to be coming from the upper side of the coil over. The coil over and spring looked always a bit tight fit and there is probably some rubbing against something there. This must be a common issue. So what could be done to make it quieter?