Paris St Germain's lead at the top of the Ligue 1 table was cut to three points after they slumped to a shock defeat at Sochaux.
Alex put the visitors in front but goals from Sebastien Roudet and Giovanni Sio put Sochaux in charge.
Blaise Matuidi levelled with 14 minutes to go but Sochaux were not to be denied and substitute Cedric Bakambu grabbed a dramatic winner eight minutes later.
PSG's slip up meant Lyon inched closer to the summit thanks to their 4-0 thrashing of Bordeaux earlier in the day.
Sochaux made a lively start and had the ball in the net inside the first 10 minutes. Sio beat Salvatore Sirigu with a superb effort but the Ivorian's strike was ruled out for offside.
With PSG struggling to deal with Sochaux's early pace the hosts went close to taking the lead when Roudet's shot had Sirigu beaten only for it to rebound off team-mate Ryad Boudebouz and go wide.
PSG then had a lucky escape in the 20th minute when the ball appeared to strike Clement Chantome on the hand in the area but referee Lionel Jaffredo waved away the home side's penalty appeals.
Sochaux's early dominance failed to pay off though and PSG took the lead against the run of play just before the half-hour mark.
Ezequiel Lavezzi saw his effort on target deflected wide and from the resulting Javier Pastore corner Alex rose above three defenders to power an unstoppable header beyond Simon Pouplin.
Sochaux hit back seven minutes later through Roudet. The French midfielder was picked out brilliantly by Boudebouz before firing a shot beyond Sirigu into the bottom corner.
Spurred on by their vociferous fans, Sochaux took the lead shortly after the restart through Sio who linked up superbly with Roudet before lashing a left-footed shot across Sirigu and into the net.
The hosts continued to press PSG and hit the woodwork on the hour mark - Sebastian Corchia whipping in a curling free-kick which beat Sirigu but not the right post.
Having created little PSG hauled themselves back into the game after 76 minutes.
Another Pastore corner caused a scramble in the box and Matuidi prodded it goalwards with Sochaux defender Jerome Roussillon getting the final touch on the line.
Sochaux were not finished and a right-wing cross from Boudebouz was cleverly knocked by Sloan Privat into the path of Bakumbu who finished clinically.
PSG pressed hard for an equaliser - Zlatan Ibrahimovic seeing two penalty shouts turned down - as Sochaux held on to move up to 14th place and inflict a fourth league defeat of the season on Carlo Ancelotti's men.