British number one Johanna Konta was knocked out of the Volvo Car Open in a shock second-round defeat by Fanny Stollar in Charleston.
Konta, 26, lost 3-6 4-6 to the 19-year-old Hungarian qualifier and world number 219.
World number 22 Konta, who had a bye in the first round, had beaten Stollar in in the Fed Cup in February, but performed well below her best.
Stollar goes on to play Kiki Bertens, the Dutch number 12 seed.
"She is really tough to play against so I was coming here expecting nothing, I was just going to play my game and focus on every point," Stollar said.