Loose barrel adjuster (road buzz makes it turn)

slowondefy2 Posts: 348
edited July 2012 in Workshop
The barrel adjuster on my rear (right) Tiagra shifter turns very easily and tends to turn on its own due to road buzz vibration, so much so that on some road surfaces I'm constantly having to retrim the rear mech. Is there a way of stiffening the thread so it won't move so easily?