Substitute Ladislas Douniama scored a last-gasp winner for Guingamp as they defeated Lens 1-0 at the Stade De La Licorne on Saturday night.
Douniama, who replaced Ronnie Schwartz in the 83rd minute, finished off a rebound from Mustapha Yatabare's powerful strike to claim three points for his side in a game which had looked destined to finish in a draw.
The result meant Guingamp bounced back from their 2-0 opening-day defeat by St Etienne while Lens, who returned to France's top tier following an appeal after a runners-up finish in Ligue 2 last season, are still in search of a win after going down 1-0 at Nantes last week.
Both sides squandered a good chance to take the lead in the first half, with Claudio Beauvue seeing a 16th-minute effort turned away by Lens keeper Rudy Riou before Adamo Coulibaly's volley struck the post at the other end shortly before the break.
Coulibaly struck wide of the mark early in the second period, with the two teams struggling to create anything.
Lens resorted to shooting from distance but Loick Landre's weak effort from 25 yards was caught easily by Samassa as the game became increasingly disappointing.
Yatabare had a rare effort on goal in the 70th minute when Sylvain Marveaux found the striker on the right side of the area but his attempted lob finished flashing over the crossbar.
However, Guingamp stole the points at the death when Riou failed to hold a powerful shot by Yatabare and substitute Douniama was on hand to score from the rebound.