The Black Cats then had a penalty appeal when Michael Chopra tangled with Alexandre Song Billong in the area but referee Keith Stroud was not convinced.
Jermaine Jenas broke through on goal and, despite being pushed outside the area, referee Graham Poll awarded a penalty for the midfielder being caught by keeper John Filan.
St Johnstone were given the chance to level when Liam Miller was adjudged to have handled in the penalty area and referee Alan Muir once again pointed to the spot.