Christian Pulisic goal was the difference as AC Milan edged to a 1-0 win over rivals Inter Milan.
Despite a controlled performance from Inter, Pulisic suddenly sent Milan ahead after the break and Cristian Chivu's side were frustrated further when Hakan Calhanoglu's penalty was superbly saved by Mike Maignan.
A derby win takes Milan into second in Serie A, while Inter drop to fourth.
Inter enjoyed a strong start to the game with Marcus Thuram tested Maignan in the early stages and they nearly had the opener when Calhanoglu fired a corner towards Francesco Acerbi, but his header smashed off a post.