Inter captain Mauro Icardi capitalised on an error from Gianluigi Donnarumma to head in an injury-time winner at San Siro.
Mauro Icardi scored a 92nd-minute winner as Inter downed rivals AC Milan 1-0 in Serie A on Sunday.
Icardi was his side's hero with a late strike that completed his hat-trick against the Rossoneri in the same fixture last season, and he once again came up trumps in the derby by heading home in added time at San Siro.
The right-wing cross from Matias Vecino was an inviting one for Icardi, but Inter's captain was fortunate Milan goalkeeper Gianluigi Donnarumma initially came to claim the ball only to misjudge the flight, leaving the striker to nod into an unguarded net.