Last year's runner-up Elena Dementieva suffered another French Open disappointment as she went down to Elena Likhovtseva in the last 16.
Likhovtseva led by a set and 3-0 before Dementieva recovered and, at 5-4 in the third, served for the match.
But the 29-year-old Likhovtseva held on to win 7-6 (7-3) 5-7 7-5, and set up a clash with Sesil Karatantcheva.
Karatantcheva - the 15-year-old conqueror of Venus Williams in round three - beat Emmanuelle Gagliardi.
The Bulgarian, who won the junior title last year, came through 7-5 6-3.
"I hope for the quarters I'll be more relaxed," she said. "I was basically scared to win."
Justine Henin-Hardenne and Maria Sharapova are also in action on Sunday.