Atalanta went to the top of Serie A when Ademola Lookman scored with three minutes remaining to beat AC Milan 2-1.
Atalanta's ninth win in a row was a fitting gift to coach Gian Piero Gasperini, who was awarded the coach of the month award earlier in the day for guiding his team to a perfect record in November.
Charles De Ketelaere put the home side ahead with a towering header after 11 minutes only for Milan to level 11 minutes later.
Theo Hernández released Rafael Leão on the right wing and his inviting cross was converted by Álvaro Morata.
Milan's Christian Pulisic left in the 38th minute because of a calf injury.
Milan looked set to end Atalanta's impressive run but Lookman nipped in at the back post to nod home a corner in the dying moments.
Atalanta has 34 points, two more than Napoli, which has a game in hand against Lazio on Sunday. Milan was in seventh place.
INTER CRUISE PAST PARMA
Serie A champion Inter defeated Parma 3-1 and extended the Milan club's unbeaten run to 13 games.
Federico Dimarco put the home side ahead five minutes before halftime when he worked a neat one-two with Henrikh Mkhitaryan and fired a low shot past Zion Suzuki.
Nicolò Barella made it two eight minutes into the second half when he finished a fast counterattack with aplomb.
Marcos Thuram's 10th goal of the season made it 3-0 in the 66th.
