Paris - Novak Djokovic celebrated his elevation to world No 1 by reaching a new personal landmark to reach the Paris Masters quarter-finals on Thursday.
The Serb won his last 16 tie with Damir Dzumhur after the Bosnian was forced to retire trailing 6-1, 2-1 at Bercy.
For second seed Djokovic it meant he extended his sequence of consecutive winning sets to 30, passing his previous best mark of 29 from 2015.
The four-time Paris champion faces Marin Cilic in the last eight on Friday.
Djokovic takes over as world No 1 in the latest ATP rankings published on Monday from Rafael Nadal, who withdrew injured from Paris on Wednesday.
Cilic, the fifth seed, secured his quarter-final ticket with a 7-6 (7/5), 6-4 defeat of Grigor Dimitrov.
Cilic fired 29 winners to advance to the last eight in the French capital for the third straight year.
The win improved the Croat's prospects of making the ATP Finals in London starting on November 11.
"I am very close to London, to securing my spot mathematically," said Cilic, who is part of the Croatia team facing France in the Davis Cup final at the end of this month.
"In the next match against Novak it will be another big challenge. (It will be) great to play him again."
Cilic, who will guarantee making the cut for London if he downs Djokovic, was ending reigning ATP Finals champion Dimitrov's season.
Dimitrov has been coached by a former coach of Djokovic, eight-time major winner Andre Agassi, in Paris this week.
Djokovic and Cilic were later joined in the quarter-finals by Karen Khachanov who saved two match points agaisnt John Isner on his way to defeating the eight-seeded American 6-4, 6-7 (9/11), 7-6 (10/8).
The Russian will next play Alexander Zverev after the German fourth seed beat Diego Schwartzman of Argentina 6-4, 6-2.
Results from the ATP Paris Masters on Thursday (x denotes seeding):
Jack Sock (USA x16) bt Malek Jaziri (TUN) 6-0, 6-4
Dominic Thiem (AUT x6) bt Borna Coric (CRO x11) 6-7 (3/7), 6-2, 7-5
Alexander Zverev (GER x4) bt Diego Schwartzman (ARG x15) 6-4, 6-2
Karen Khachanov (RUS) bt John Isner (USA x8) 6-4, 6-7 (9/11), 7-6 (10/8)
Kei Nishikori (JPN x10) bt Kevin Anderson (RSA x7) 6-4, 6-4
Roger Federer (SUI x3) bt Fabio Fognini (ITA x13) 6-4, 6-3
Marin Cilic (CRO x5) bt Grigor Dimitrov (BUL x9) 7-6 (7/5), 6-4
Novak Djokovic (SRB x2) bt Damir Dzumhur (BIH) 6-1, 2-1 - retired