Paris Saint-Germain suffered their first home league defeat in 35 matches as second-half goals from Vagner Love and Fabinho earned Monaco a surprise 2-0 win at the Parc des Princes.
Laurent Blanc's side were, of course, crowned Ligue 1 champions for a fourth successive time last weekend, with two months of the season still left to play.
But their homecoming party fell flat as second-placed Monaco avenged the 3-0 defeat they suffered in the corresponding fixture at Stade Louis II back in August.
Leonardo Jardim's men had travelled north boasting an impressive record of just one defeat in their last 12 league games against the capital club.
But they looked destined to suffer a heavy defeat having been totally outplayed in the first half.
They were a different side after the break, however, with Love's close-range finish and Fabinho's penalty securing their first win in four games and extending the gap between themseleves and third-placed Nice to five points.
PSG almost took the lead in the fourth minute when Edinson Cavani saw his volley from a Marquinhos cross brilliantly parried at point-blank range by Danijel Subasic.
In the ensuing scramble, Zlatan Ibrahimovic did manage to force the ball into the net, but his effort was ruled out for offside.
Moments later, Cavani came within inches of sliding home a superb ball whipped across the face of goal by Angel Di Maria.
Monaco's five-man defence was really struggling to cope with PSG's attacking movement and survived another scare on 21 minutes when an intricate passing move created an opportunity for Cavani, but Ricardo Carvalho managed to block the Uruguayan's goalbound strike.
Cavani's next effort was an acrobatic bicycle kick that flashed over the bar and, shortly afterwards, only Elderson Echiejile's head kept Di Maria's shot from finding the net.
The occasional breakaway apart, the visitors found themselves on the back foot for the entire first half and would have been delighted to go into the break on level terms.
Monaco improved significantly at the start of the second half, however, as PSG seemed to take their foot off the gas.
Tiemoue Bakayoko and Thomas Lemar both drew saves from Kevin Trapp before Love stunned the home fans by firing his side in front on 65 minutes.
Lemar raced away down the left and drilled in a low cross which Love converted from close range.
Three minutes later, Fabinho made it 2-0 from the penalty spot.
David Luiz was too casual in trying to clear his lines and, after being dispossessed by Fabinho, hauled the Brazilian down.
The 22-year-old took responsibility himself and calmly sent Trapp the wrong way.
Ibrahimovic and Cavani both went close with late headers for the hosts, but Monaco held out to secure a hard-earned victory in the champions' back yard.
