Novak Djokovic came out strong in his opening match in Madrid on Tuesday, defeating Gael Monfils, 6-3, 6-2, to move through to the round of 16 at the Masters 1000 event.

With the win, Djokovic added yet another record to his resume: he’s now 18-0 against Monfils, the best undefeated tour-level head-to-head record for a man in the Open Era. Going into the match, Djokovic was part of a six-way tie for the record at 17-0.

18-0: Novak Djokovic vs Gael Monfils
17-0: Rafael Nadal vs Richard Gasquet
17-0: Roger Federer vs David Ferrer
17-0: Roger Federer vs Mikhail Youzhny
17-0: Ivan Lendl vs Tim Mayotte
17-0: Bjorn Borg vs Vitas Gerulaitis

It’s worth noting that before their now-18 tour-level meetings, Monfils did get one victory over Djokovic in the Challengers, defeating the Serb in the quarterfinals of a clay-court event in Bergamo, Italy in 2004 (Djokovic was a No. 600-ranked 16-year-old at the time, while Monfils was a No. 669-ranked 17-year-old).

Monfils also won the pair’s only junior meeting earlier that year.

Djokovic’s win on Tuesday was also his 375th career win at a Masters 1000 event, second only to Nadal (403), and the 995th tour-level win of his career, fifth only to Jimmy Connors (1,274), Federer (1,251), Lendl (1,068) and Nadal (1,048).

The Serb also secured his stay at No. 1 on the ATP rankings with the win—had Monfils beaten him, Daniil Medvedev would have returned to the top spot.