Monaco missed the chance to go six points clear at the top of Ligue 1 after being held by Bastia.
The Corsican side took the lead when Guinean Sadio Diallo beat goalkeeper Danijel Subasic from close range.
But Portugal midfielder Bernardo Silva pulled the league leaders level early in the second half when he headed in an Almamy Toure cross.
Champions Paris St-Germain would move to within a point of the summit should they beat Toulouse on Sunday.
Monaco travel to face Manchester City in their Champions League last-16 first-leg game on Tuesday.
Support InfoStride News' Credible Journalism: Only credible journalism can guarantee a fair, accountable and transparent society, including democracy and government. It involves a lot of efforts and money. We need your support. Click here to Donate