Partick Thistle 1-2 Celtic
Paul Lambert got Celtic off the mark
Celtic were made to work hard before finally claiming all three points from Partick Thistle at Firhill.
It appeared that Celtic would have things their own way when Paul Lambert gave them an eighth minute lead.
But Thistle fought back and scored a deserved equaliser through James Grady.
Alan Thompson scored the winning goal from the penalty spot, though, two minutes before the break after Stilian Petrov was adjudged to have been fouled in the box.
Celtic started the stronger of the two sides and Shaun Maloney passed up an early chance after finding himself clean through on goal, his weak effort saved by Jakup Mikkelsen.
But Mikkelsen was to blame minutes later when Stilian Petrov cut the ball back for Lambert, whose low drive squirmed under the keeper's hand and over the line.
A lapse from Bobo Balde almost let Ian Ross in for a quick equaliser, but he shot wide under pressure.
But Thistle did get back on level terms on 26 minutes after a fine lay-off by Gerry Britton allowed Grady to sneak in behind Joos Valgaeren and toe-poke the ball past Rab Douglas.
There was a scare for Thistle 10 minutes before half time when Petrov went down in the box as David Rowson clipped his heels, but referee Kenny Clark ruled it to have been accidental.
James Grady pulled Thistle level
Moments later, Derek Whyte made a vital challenge on Balde as the Celtic defender prepared to pounce at the back post.
But with three minutes remaining in the first half, Clark did award the visitors a penalty as Ross and Petrov collided, and Thompson made no mistake from the spot.
Thistle were by no means out of the game and the second half began with neither team able to make any great impact on the opposition defence.
Thompson eventually forced a save from Mikkelsen with a blistering drive from 25 yards, which the keeper did well to hold.
Celtic substitute Liam Miller then tested Mikkelsen from the edge of the box, but the Faroese international gathered at the second attempt.
The visitors stepped up the pressure and Petrov fired just wide after 67 minutes.
Thistle continued to scrap away and might have grabbed an equaliser during a goalmouth scramble in the closing minutes before Douglas eventually dived on the ball to secure the points for Celtic.
Partick: Mikkelsen, Anis, Murray, Whyte, Forrest, Rowson,
McBride (Mitchell 67), Ian Ross, Grady, Thomson (Bonnes 72),
Subs Not Used: Arthur, Andy Ross, Panther.
Booked: Anis, Whyte.
Celtic: Douglas, Balde, Varga, Valgaeren (Miller 62), McNamara,
Lennon, Lambert (Sylla 78), Petrov, Thompson, Larsson, Maloney.
Subs Not Used: Hedman, Beattie, Petta.
Ref: K Clark