Mauro Icardi’s stoppage-time goal clinched Inter Milan a 1-0 win against arch rivals AC Milan at a sold-out San Siro.
Inter skipper Icardi, whose last-minute penalty won the corresponding fixture for his side last season, headed home in the second minute of time added on.
Luciano Spalletti’s side secured their fifth straight Serie A win and remain third in the table, six points behind leaders Juventus.
The 222nd Milan derby failed to provide much quality or entertainment for a crowd of 78,725, but both sides had a goal disallowed, while Inter defender Stefan de Vrij’s first-half shot hit a post.
After a slow start, Icardi thought he had given Inter a 12th-minute lead when he turned home Matias Vecino’s flick-on from close range.
But after a brief check with the video assistant, referee Marco Guida ruled that Icardi had been offside.
Milan midfielder Franck Kessie fired wide from inside the penalty area and, at the other end, Ivan Perisic’s header from Sime Vrsaljko’s cross was comfortably saved by goalkeeper Gianluigi Donnarumma.
Inter went close to breaking the deadlock in the 34th minute. Vrsaljko’s corner was headed on to De Vrij and the latter’s effort from eight yards out rebounded off the woodwork.
Donnarumma was then forced into action again as he held Vecino’s 20-yard shot, but Inter enjoyed their best spell just before half-time.
Matteo Politano crashed a shot from outside the area over the crossbar and Milan skipper Alessio Romagnoli produced a brilliant block to keep out Icardi’s effort.
Milan defender Mateo Musacchio briefly thought he had broken the deadlock when turning home at the back post, but he was also ruled offside by Guida.
Inter then spurned a golden chance when Vecino blasted Perisic’s cut back to the penalty spot off target.
Both sides wasted possession in the second half and created few chances.
Donnarumma was forced to react quickly to clear Lucas Biglia’s back-pass before Vecino headed over from six yards.
Suso lashed Milan’s first effort on target straight at goalkeeper Samir Handanovic in the 81st minute before the late drama unfolded in added time.
Vecino found space on the right and his brilliant cross was met by Icardi, who escaped the covering defence with some neat movement and planted a firm header beyond Donnarumma.
Defeat has left AC Milan in 12th place, with just three wins from their first eight matches.