Czech Republic forward Roman Bednar struck a late winner to earn Hearts a 2-1 win over champions Celtic at Tynecastle.
Bednar had opened the scoring on 50 minutes with an angled shot from the left which beat keeper Artur Boruc and clipped the inside of the right post.
Celtic levelled after a sweeping move from defence was completed by Bulgarian Stilian Petrov lashing a left foot shot into the top left hand corner from 18 metres after 65 minutes.
Hearts snatched the points three minutes from time when Celtic substitute Neil Lennon's poor backpass from just inside his own half was pounced on by Bednar who beat Boruc to the ball and slotted home.
Hearts, St Mirren and Falkirk have maximum six points from two games.