Paris Saint-Germain moved level on points with second-placed Monaco thanks to a 2-1 win at Nancy.
First-half goals from Lucas Moura and Edinson Cavani looked set to kick-start an emphatic evening for the champions, but Alou Diarra's 55th-minute strike made it an uncomfortable finish for Unai Emery's men.
The Parisian giants wasted little time in stamping their authority on the game. With 13 minutes on the clock Lucas' free-kick evaded everyone, including Nancy goalkeeper Guy N'dy Assembe, before bending in the goal.
Five minutes later Cavani made it two, cleverly lifting the ball over N'dy Assembe after Michael Chretien made a hash of keeper Alphonse Areola's long kick.
Nancy could easily have pulled one back before the interval when Lucas needlessly gave away possession but, from the resulting break, Areola got a firm hand to Anthony Koura's stinging effort.
However, 10 minutes after the restart the hosts did haul themselves back into the game. Diarra rose above Cavani in the area to powerfully head Benoit Pedretti's free-kick beyond Areola.
Buoyed by that strike, the home crowd urged their side forward, but Nancy struggled to create further changes.
At the other end Cavani flashed a volley over the crossbar.
Christopher Mandanne went down too easily inside the area late on and the only reward the substitute got for his troubles was a yellow card.