Gennaro Gattuso's first game in charge of AC Milan ended with Benevento goalkeeper Alberto Brignoli scoring a 95th-minute equaliser to earn the home side their first ever Serie A point.
Milan winger Giacomo Bonaventura opened the scoring for Milan in the first half before the hosts struck back through George Puscas.
Nikola Kalinic then restored Milan's goal advantage with a header, capitalising on the home side's struggle to clear the ball from a corner, but it would be the Benevento goalkeeper who had the final say.
Deep into the five minutes of stoppage time added onto the end of the game, a free-kick from Danilo Cataldi was met by the head of Brignoli who had been sent into the opposing penalty area to attack the set-piece.