Polish striker Maciej Zurawski's first-half goal secured Celtic a 1-0 win over Old Firm rivals Rangers at Ibrox to extend their lead at the top to 13 points.
Zurawski drilled a low angled first time shot wide of keeper Ronald Waterreus from 15 metres after 11 minutes.
Belgian midfielder Thomas Buffel wasted a glorious chance to level 10 minutes from halftime when he opted to pass instead of shoot and Croat Dado Prso failed to convert from a tight angle a minute from time.
Celtic have 64 points from 26 matches, ahead of Hearts on 51. Rangers, who will part with manager Alex McLeish at the end of the season, remain fourth on 43 points.
Celtic manager Gordon Strachan described the 13-point lead as 'quite encouraging.'
His decision to play Roy Keane and Neil Lennon in the centre of midfield was decisive. Strachan rested Shunsuke Nakamura but the Hoops won the battle in the centre of the field.
But man-of-the-match Keane admits he is still not guaranteed a starting place despite his display.
He enthused: 'It was nice to get 90 minutes under my belt but the priority was to win the game. It is nice (to have 100% Old Firm record) but my record isn't important. It is important to win the league after last year.'
'I've played in some big games before so it wasn't really a shock to me. I have played here before with United so I knew what it would be like. You enjoy it and enjoy it more when you win. You expect it to be quick and passionate like any derby match.'
