Paris Saint-Germain suffered a surprise 1-0 defeat to Nancy at the Parc des Princes, only the Ligue 1 leaders' second defeat of the season.
The winning goal came four minutes into the second half, defender Jean Calve's shot beating PSG keeper Salvatore Sirigu.
Despite the loss PSG remain top of Ligue 1 on goal difference from Montpellier, but the points were valuable for struggling Nancy, who moved out of the relegation zone.
Brest put some breathing space between themselves and the bottom three in Ligue 1 with a 2-0 victory over 10-man Sochaux.
Bruno Grougi scored the opener from the penalty spot following a challenge which saw Mathieu Peybernes sent off, with Romain Poyet adding another 10 minutes from time as the home side picked up only their second league win of the season.
Valenciennes edged clear of the relegation zone in Ligue 1 with only their third win of the season, a 2-1 home triumph over Auxerre. Alain Traore gave the visitors the lead 11 minutes before the interval, but Isimat Mirin and Mamadou Samassa struck in the second half to secure a much-needed win.