The Scot beat Stephen Harbinson from 12 yards with a well taken left-foot effort after taking the ball past defender Paul Bradley.

Seven minutes before that Celtic striker Paul McVeigh had squandered a glorious opportunity to grab their first goal in over a month.

He failed to convert a spot-kick awarded after Gareth McKeown had upended James Lavery when David Miskelly correctly dived to his right to turn the ball around a post.

Celtic came close again on 50 minutes when Lavery hit the bar followed by a Bradley effort cleared off the line.

For the Ports Kevin Braniff forced a superb stop from Harbinson on 86 minutes.