Romain Hamouma's second-half strike proved the difference as St Etienne went to the top of Ligue 1 with a narrow 1-0 victory over fellow high-flyers Valenciennes.
Both sides had the chance to move to the top of the standings, level on points with Lyon, with a win, but it was the hosts who prevailed as they extended their unbeaten run to nine matches.
They dominated throughout at the Stade Geoffroy-Guichard and deservedly sealed all three points when Hamouma netted after Valenciennes had failed to clear their lines in the 73rd minute.
The two teams have been the surprise challengers this season, although St Etienne midfielder Renaud Cohade was not willing to rest on his laurels against a team who had lost just once in their last seven matches before tonight.
But any hopes of a clash to savour were dashed in a first half of relatively few clear-cut chances.
Pierre-Emerick Aubameyang volleyed wide of the target from just outside the area, while at the other end Valenciennes midfielder Mathieu Dossevi evaded the challenges of several home defenders and burst into the area, although he lost his footing at a crucial point and could only direct a tame shot at Stephane Ruffier.
Dossevi then brilliantly tracked back to stop Max Gradel from latching on to Francois Clerc's cross, while Aubameyang was denied from a narrow angle by Valenciennes goalkeeper Nicolas Penneteau.
St Etienne, perhaps sensing an opportunity at home, upped the ante in the second half, with Aubameyang once again thumping over before forcing Penneteau to make two fine saves.
But there was nothing the Valenciennes keeper could do when Hamouma netted following a goalmouth scramble 17 minutes before the end, with the midfielder firing home after a flick-on from Cohade.
They managed to hang on to their lead to ensure they top the table for the next 24 hours at least.