World number one Djokovic, aiming to become the first man in 43 years to hold all four grand-slam titles at the same time, rattled off the first seven games before faltering against Slovenian Blaz Kavcic.
"I stopped," the Serbian told a news conference, after the match turned into a fierce battle which he finally won 6-0 6-4 6-4. "I gave him the opportunity to come back into the match after a perfect first seven games."
The fans sitting in the sunshine on Suzanne Lenglen court threw themselves behind underdog Kavcic and the Slovenian played on their sympathy, urging them on when they cheered his first game win at the start of the second set.
Their noisy enthusiasm reached a high point after he saved a breakpoint to hold for 3-3 in the third set and then went 0-30 up in the next game, and the umpire sternly warned the crowd to keep quiet during play.
In the third round, Djokovic will play French qualifier Nicolas Devilder while Federer will meet either Slovakian Martin Klizan or Frenchman Nicolas Mahut.
In Image: Novak Djokovic of Serbia celebrates winning his second round match against Blaz Kavcik of Slovenia