Romain Hamouma's second-half strike was enough for St Etienne to beat Evian and move up to into third place in Ligue 1.
Lyon have the chance re-take the position when they meet Reims later on Sunday, but the win maintained the home side's excellent form with Christophe Galtier's men having yet to lose a league game in 2013.
Evian came into the game in good form having picked up eight points from four games, including wins over Lille and Sochaux, to move out of the Ligue 1 relegation zone.
However poor early-season form meant they were just a point clear of the bottom three and desperate to keep their good momentum going.
It was the home side who started quickly and goalkeeper Bertrand Laquait was called into action after 15 minutes to punch away Pierre-Emerick Aubameyang's effort.
Three minutes later Evian had their first opportunity, but from 25 yards Cedric Barbosa shot straight at Stephane Ruffier.
A Fabien Lemoine volley from 20 yards again tested Laquait, before the stopper was once again called into action just after the half-hour to tip away Hamouma's effort.
With half-time approaching Aubameyang played in Yohan Mollo, those thundering effort clattered into the post.
Five minutes after the restart Laquait had to be in top form to keep out dangerman Aubameyang, who was searching for his 18th Ligue 1 goal of the season.
However there was little the stopper could do to keep out what was to be the winner.
With 12 minutes left a Renaud Cohade cross was not cleared by the visiting defence and from five yards Hamouma headed home his fifth goal of the season.
With two minutes left, Evian should have snatched a leveller, but from just inches out substitute Yannick Sagbo headed Saber Khlifa's cross over the bar.