For 72 minutes Partick Thistle looked capable of continuing their unbeaten run and becoming the first side to take points from Celtic this season, then Henrik Larsson struck.
Hoops boss Marin O'Neill had other ideas, going for broke by introducing John Hartson as a second-half substitute and watching proudly as the Welshman created the winning goal for Larsson.
Earlier Neil Lennon's appearance in the Celtic team following his midweek death threat was a welcome sight for all football fans, while fellow midfielder Stilian Petrov was rested for Wednesday's Champions League qualifier in Switzerland.
Thistle enjoyed the moral victory of winning an early corner but that was a rare backward step for the visitors. Moments later a serious blunder by former Celtic defender Derek Whyte gave the ball to Larsson and although he skinned one defender his right-foot drive was blocked and the rebound flashed narrowly wide.
Partick also survived two penalty claims, the first when Alan Archibald seemed to deflect Didier Agathe's cross with his arm, the second when Chris Sutton tumbled inside the box.
After 31 minutes a perfect square pass by Larsson set up Paul Lambert 20 yards from goal only for the Scotland skipper to shoot wide. Lambert, together with Jackie McNamara, returned the compliment shortly before half-time but Larsson brushed the side netting from eight yards.
Chances continued to arrive for Celtic after the break and only a clumsy first touch by Sutton saved Thistle following Larsson's inch-perfect head flick. Sutton was again wasteful in the 57th minute, blasting Agathe's cutback yards over the crossbar.
Hartson then came on to form a three-man attack and with 18 minutes left the Welshman's cross with the outside of his right boot enabled Larsson to knock the ball home from point-blank range