Scott Sinclair came off the bench to score the winner on his Celtic debut as the Scottish champions recorded a 2-1 win at Hearts.
The winger's signing from Aston Villa was only confirmed earlier on Sunday, but his late strike proved decisive after James Forrest and Jamie Walker had exchanged first-half goals at Tynecastle.
Celtic made a great start when Forrest linked up with Callum McGregor before curling a low left-footed strike into the far corner from 18 yards in the eighth minute.
Hearts wasted a golden chance to equalise when Tony Watt somehow failed to hit the target with a close-range header against his former club, while Leigh Griffiths should also have done better with an attempted chip after being sent through at the other end.
But Hearts were level nine minutes before the break when Walker was adjudged to have been brought down by Kieran Tierney and he calmly stepped up to send Celtic goalkeeper Craig Gordon the wrong way from the spot.
Another Griffiths effort was dramatically cleared off the line by Igor Rossi after Moussa Dembele had his shot saved by Jack Hamilton in the Hearts net.
Sinclair came on for his maiden Celtic appearance as a substitute with 29 minutes remaining and he netted the winner with nine minutes of an otherwise quiet second half remaining.
Griffiths made ground down the left and the onrushing Sinclair raced in to get on the end of his team-mate's delivery and net the winner from six yards.