Perhaps with one eye on the Champions League, Ligue 1 leaders Monaco dropped points in the title race after drawing 1-1 away to struggling Bastia.
Monaco needed a second-half header from Portugal midfielder Bernardo Silva, after Guinean forward Sadio Diallo gave the home side the lead with a first-half goal validated by goal line technology.
Although the draw moved Monaco four points clear, defending champions Paris Saint-Germain can trim the lead to one by beating Toulouse at home on Sunday.
Monaco, who travel to play Manchester City in the first leg of their round of 16 match on Tuesday, started slowly against Bastia.
The Corsican side deservedly took the lead in the 19th minute when Monaco's defense was caught out by a deep cross to the back post and forward Sadio Diallo's close-range header was ruled to have crossed the line by referee Clement Turpin, thanks to goal line technology.
Monaco ended the half well, however, with Portugal midfielder Joao Moutinho and striker Radamel Falcao having shots saved by Bastia goalkeeper Jean-Louis Leca.
Silva equalised in the 52nd minute, timing his run to head past Leca from close range to extend Monaco's unbeaten run to 12 games.
Monaco, who have netted 108 goals in all competitions, had late chances with substitute Kylian Mbappe twice going close and midfielder Thomas Lemar blazing over.
Bastia remained in 19th place.