Champions Celtic made it five Scottish Premiership wins out of five and consigned St Mirren to a season’s first league defeat after coming from behind in Paisley.
Liam Scales’ header and Yang Hyun-jun’s calm finish overturned the hosts’ half-time advantage, obtained through Nikolas Agrafiotis’s penalty.
Scales had conceded the spot-kick when his fist blocked Chris Mochrie’s volley, with referee Ryan Lee showing no hesitation in pointing to the spot.
Camilo Duran netted from a Yang cross but VAR ruled offside on a very marginal call as the Paisley side’s lead held until the break.
Luke Thomas could not direct his effort on target as St Mirren opened up their visitors in search of a late leveller, and fellow substitute Shim Mheuka was denied a first Celtic goal by another VAR offside.
Martin O’Neill’s side are top on 15 points, five points above Craig McLeish’s St Mirren and Rangers.
St Mirren analysis: Buddies battle hard
St Mirren competed well against the league leaders, particularly in the first half.
Winger Ismeal Kabia set up an intriguing battle with Colby Donovan, with the Celtic right-back booked for an early foul and knowing he could not mis-time any later challenges.
Fraser Taylor’s low shot from distance tested Viljami Sinisalo prior to the penalty and Taylor had another decent attempt deflected wide at 1-1. Mochrie should have at least hit the target from Declan John’s corner soon after.
The Scales equaliser perhaps drew questions over Jacob Chapman’s positioning but the goalkeeper had an otherwise solid game and was left exposed as Yang ran through for Celtic’s winner.
Substitute Thomas and Paul Nsio got the home crowd going when they tested Sinisalo and Thomas should have led with his right foot instead of his left when presented with his late opportunity.
With 10 points, McLeish’s side are still in a highly desirable position after five league fixtures before visiting Rangers on Wednesday (19:45 BST).
Celtic analysis: Duran turns provider
After six goals in his previous five games, it looked like it would not be Duran’s night in the fading Paisley light.
His low shot was held by Chapman in Celtic’s immediate response to the opening goal and, after the VAR offside decision, Duran was denied at close range moments after Callum McGregor’s volley had been turned out by the St Mirren keeper.
However, the Colombian showed tenacity to win the ball in St Mirren’s half in advance of his assist. Mheuka would take over from Duran and, as well as his offside goal, fired over.
Scales atoned for his earlier spot-kick concession by superbly heading in Benjamin Nygren’s corner and almost mirrored that goal from the opposite side.
Calvin Ramsay brilliantly stopped a certain second Celtic goal when blocking Yang’s shot after Chapman had been eliminated by Nygren’s pass, but Yang would have the last laugh.
His replacement Sebastian Tounekti lacked composure with a similar chance he put wide wide.
A trip to Perth to face St Johnstone beckons on Wednesday (20:00), a first McDiarmid Park visit for 16 months for the club and O’Neill’s first return to Perth as Celtic manager in 25 years.
