Lautaro Martinez scored the only goal as Inter Milan beat city rivals AC Milan at the San Siro.
Second-placed Inter remain 13 points behind Serie A leaders Napoli, who won 3-0 at Spezia earlier in the day.
Captain Martinez headed the only goal of the game from a corner by former Milan midfielder Hakan Calhanoglu.
Inter had two goals disallowed late on - substitute Romelu Lukaku's effort was ruled out for a foul on Malick Thiaw and Martinez's strike for offside.