MELBOURNE, Australia (AP) — Coco Gauff kept alive her hopes of back-to-back Grand Slam singles titles after beating Marta Kostyuk 7-6 (6), 6-7 (3), 6-2 in an error-strewn quarterfinal match at the Australian Open on Tuesday.

The U.S. Open champion had 51 unforced errors, nine double faults and just 17 winners but battled past Kostyuk in three hours, eight minutes.

The 19-year-old American has now won 12 straight matches in Grand Slams.

“I’m really proud of the fight I showed today,” said Gauff, who plays either defending champion Aryna Sabalenka or ninth-ranked Barbora Krejcikova in the semis.