Gary Hooper and Ki Sung-Yueng scored in a minute stretch of the second half and Celtic won its seventh straight match 0 over St. Johnstone on Sunday at McDiarmid Park.
Hooper scored in the 60th minute and Ki followed in the 64th, as Celtic moved its unbeaten streak to 10 matches and moved back within four points of leader Rangers after 19 matches. Rangers defeated Inverness, 2-1, on Saturday.
Celtic opened the scoring when Hooper drove a shot to the lower right from the edge of the 6-yard box for his 11th goal of the season, and Ki picked out the upper-left corner from about 12 yards out for his fifth goal this season.
The Bhoys posted their fifth shutout in their last six league matches.
St. Johnstone lost its third straight, and is 22 points off the pace in fourth place.