Fifth seed Ons Jabeur produced another gutsy display to reach the US Open last 16 with a three-set win over Marie Bouzkova that took almost three hours.
Jabeur, last year's runner-up, won 5-7 7-6 (7-5) 6-3 on Arthur Ashe Stadium against Czech 31st seed Bouzkova, who was hampered by a thigh injury.
Tunisia's Jabeur, 29, has been struggling with illness in New York.
"Hopefully I'll continue with this warrior symbol," she said after the longest women's match at this event.
"I love fighting. I trust my body. I know I can go all the way playing three sets, no problem.