Paris St-Germain's winless run in the Champions League extended to three games as they were beaten at home by Atletico Madrid.
Angel Correa struck in the third minute of added time at the end of a hard-fought clash to snatch victory for the Spaniards.
PSG midfielder Warren Zaire-Emery, 18, became the youngest player in the competition's history to start 15 games - and marked the occasion with an early opener.
It came in the 14th minute after Atletico defender Clement Lenglet suffered a lapse in concentration that allowed his former Barcelona team-mate Ousmane Dembele to steal the ball just inside the penalty area. The French winger laid the ball off to Zaire-Emery who beat Jan Oblak with a delicate dink.
The Spanish side equalised four minutes later when Nahuel Molina slammed the ball past Gianluigi Donnarumma from close range after their hosts failed to clear.
PSG continued to dominate the ball and put the visitors under increased pressure as the second half went on, with Bradley Barcola and Achraf Hakimi forcing Oblak into smart stops.
Diego Simeone's side also pushed for a winner and substitute Correa got it in dramatic fashion with a low strike past Donnarumma.
PSG are 25th in the table with four points after four games, while Atletico are two places above them on six points.
On match day five PSG will travel to Germany to face Bayern Munich, while Atletico Madrid visit Sparta Prague.
Watch highlights of every Champions League game from 22:00 on Wednesday on BBC iPlayer and the BBC Sport website and app.
There will also be a Champions League Match of the Day on BBC One on Wednesday, from 22:50 to 00:10.