Top seed Maria Sharapova needed three sets before seeing off Bethanie Mattek on Philippe Chatrier court.
The Russian was a set up when her match was suspended on Thursday evening due to bad light.
Resuming 3-2 down in the second set, she lost her way and allowed Mattek to take it to a decider but Sharapova won out 6-2 3-6 6-2.
The new world number one will meet Italy's Karin Knapp, the 32nd seed, in the third round.
