Paris St-Germain suffered their first Ligue 1 defeat of the season as they were beaten by struggling Strasbourg.
Nuno da Costa headed the hosts, who move up to 14th, into the lead.
Kylian Mbappe, back in the starting line-up after being dropped to the bench in midweek, equalised from Adrien Rabiot's pass.
But Stephane Bahoken scored the winner, smashing home after da Costa flicked on a long ball from goalkeeper Bingourou Kamara.
PSG had chances to win during nine minutes of stoppage time when Rabiot forced a save from Alexandre Oukidja, who replaced the injured Kamara, and then Mbappe fired over from close range.
The capital side are 10 points above second-placed Marseille, who visit Montpellier on Sunday.