Lorenzo Musetti has been warned for unsportsmanlike conduct for kicking a tennis ball that inadvertently hit a linesperson during his French Open quarterfinal against Frances Tiafoe.

Lorenzo Musetti advanced to his first semifinals appearance at the French Open Tuesday with a four-set win over Frances Tiafoe. Musetti held off Tiafoe despite receiving an unsportsmanlike conduct warning in the second set after inadvertently hitting a line judge with a ball he kicked toward the back wall at Roland-Garros out of frustration.

Frances Tiafoe hadn’t dropped a set on the way to the French Open quarterfinals, but he wasn’t up to the task against Lorenzo Musetti.