French world number 31 Alize Cornet was given a code violation for taking her shirt off on court during her US Open first-round defeat by Johanna Larsson.

Cornet changed her shirt during the break between the second and third sets, but realised it was back-to-front and quickly switched it on court.

But the chair umpire gave her a warning – despite male players being permitted to change their shirts on court.

Cornet lost 6-4 3-6 2-6 to Sweden’s Larsson in the searing New York heat.

On Tuesday, temperatures close to 38C (100F) at Flushing Meadows were made more stifling by humidity levels of over 50%, with five male players forced to retire due to heat-related issues.

The Women’s Tennis Association’s (WTA) rules state female players are not permitted to change their clothing on court, and instead must do it in a dressing room.

Male players regularly change their shirts on court at the change of ends.

• Live scores, schedule and results
• Alerts: Get tennis news sent to your phone