The veteran defender gathered the ball 30 yards out, held off the challenge of BrahimHemdani and sent a looping volley high beyond the flailing fingertips of McGregor.
Rangers were seldom seen as an attacking threat and their only sight of goal in the first half came when Sebo turned nicely on a BrahimHemdani pass only to shoot tamely at Artur Boruc.
Rangers goalkeeper Neil Alexander was then called into action when BrahimHemdani lost possession just outside the box and the ball broke to Aleksandr Anyukov whose smart shot was initially fumbled and then held by Alexander.