Three teams share the lead in Ligue 1 heading into Christmas after Marseille joined Lyon and Paris St Germain at the summit by beating St Etienne 1-0.
In what is turning into one of the most exciting title races in years, Elie Baup's men were once again indebted to one of the Ayew brothers - Andre on this occasion - as they kept themselves in the thick of things.
Ayew scored the only goal of the game on the stroke of half-time to see off Les Verts, who themselves have gone from title contenders to mid-table fodder over the past month.
They are now 11 points behind the leading trio, who are headed by PSG on goal difference, and were guilty of failing to test home goalkeeper Steve Mandanda enough.
Valenciennes ended an encouraging first half to the Ligue 1 season on a high note with a hard-fought 2-1 win over 10-man Evian.
Goals from Gregory Pujol and Jose Saez saw the hosts to a victory that means they will spend the winter break inside the top six.
Saber Khelifa equalised for Evian in the first half but they had no response to Valenciennes' second goal, which came just moments after the visitors had lost Djakaridja Kone to a 71st-minute red card. VA's Mathieu Dossevi also missed a second-half penalty for the hosts.
Sochaux remain in the relegation zone after slipping to their fifth away defeat of the season, 2-0 at Toulouse.
Adrien Regattin put the hosts in front in the first half with a superb free-kick and Emmanuel Riviere sealed the win five minutes from time.