Virgil van Dijk's impressive early goal was enough to defeat St Johnstone and move Celtic 11 points clear at the top of the Scottish Premiership.
The Dutch defender beat several St Johnstone players on his way to firing Neil Lennon's side ahead.
Anthony Stokes had a shot blocked as the visitors dominated the first half.
Saints improved after the interval and Gwion Edwards tested goalkeeper Fraser Forster with a powerful shot from inside the penalty area.
But the Perth side could not find a leveller and points dropped by Aberdeen, Dundee United and Inverness allowed Celtic to stretch their advantage.
Van Dijk celebrates his winning goal
The hosts tried to break quickly using the pace of Stevie May in the first few minutes but it was his marker who opened the scoring.
Van Dijk collected the ball on the halfway line, waltzed past a handful of players as he dribbled forward and drilled a low shot past goalkeeper Alan Mannus.
The net bulged again when Stokes converted Scott Brown's low cross but the offside flag had been raised against the latter, although television replays suggested the Celtic captain may have been onside.
Celtic continued to exert control and Stokes latched on to a long ball and got past the advancing Mannus only to have his shot blocked as St Johnstone players tried frantically to get back.
And van Dijk threatened a second when he headed wide from a corner.
St Johnstone knew they had to improve in the second half and Tommy Wright sent on winger Edwards in place of defender Gary Miller.
May went down in the box as he tussled with van Dijk but referee Craig Thomson was unmoved by the forward's penalty appeal.
A nice turn and pass by Nigel Hasselbaink created a shooting opportunity for Brian Easton on the left angle of the box but van Dijk got across to block.
Edwards was next to have a run at the Celtic defence and, after speeding down the left and cutting inside, his fierce drive had to be dealt with by Forster.
Celtic's play was lacking the fluency so apparent in the first half but Kris Commons almost doubled their lead with an excellent snapshot that Mannus kept out with an equally impressive save.
And there was to be no further scoring as the visitors saw out victory.
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