Kylian Mbappe's two goals against his former club were not enough as French Ligue 1 leaders Paris Saint-Germain blew a 2-0 lead to lose 3-2 at Monaco.
Mbappe's first-half brace took him to 99 goals for PSG since joining from Monaco three years ago.
Lively German forward Kevin Volland netted twice after the break, and was fouled by centre half Abdou Diallo for a penalty converted by midfielder Cesc Fabregas in the 83rd.
Diallo was sent off to leave PSG with 10 men in the closing stages.
The defeat was PSG's third of the season and ended a run of eight straight wins after losing their first two games.
Monaco moved up to second place, four points behind PSG, despite being without top scorer Wissam Ben Yedder as he recovers from the coronavirus.
Another comfortable PSG win looked on the cards when Mbappe latched on to a fine pass from winger Angel Di Maria and finished confidently in the 24th minute.
The France striker then beat goalkeeper Vito Mannone from the spot in the 36th after midfielder Youssouf Fofana gave away a penalty.
Striker Moise Kean and Mbappe had goals ruled out for offside shortly before the break, and Monaco pulled one back in the 51st when Volland turned in Fofana's cross from the right.
Volland pounced again in the 64th when Fabregas set him up from close range and Fabregas scooped over a shot 10 minutes later as Monaco found another gear.
In Friday's other game, Rennes missed the chance to move into second after losing at home to Bordeaux 1-0, with winger Hatem Ben Arfa punishing his former team with the only goal.
Ben Arfa, who scored nine goals for Rennes two seasons ago, struck in the 36th after cutting past three defenders on the left and smacking in a diagonal shot.
It was the former France international's seventh career goal against Rennes, his best against any side.
The defeat dropped Rennes to fifth place, while inconsistent Bordeaux climbed to 11th.
Australian Associated Press