Five-time Grand Slam champion Iga Swiatek accepted a one-month suspension after testing positive for the banned substance trimetazidine, a heart medication known as TMZ, the International Tennis Integrity Agency announced Thursday.

Swiatek failed an out-of-competition drug test in August, and the ITIA accepted her explanation that the result was unintentional and was caused by the contamination of a nonprescription medication, melatonin, that Swiatek was taking for issues with jet lag and sleeping.

It was determined her level of fault was “at the lowest end of the range for no significant fault or negligence,” the IATA said.

This is the second recent high-profile doping case in tennis: The top-ranked man, Jannik Sinner, failed two tests for a steroid in March and was cleared in August, right before the start of the U.S. Open, which he went on to win for his second Grand Slam title of the season.

Swiatek is a 23-year-old from Poland who was ranked No. 1 most of the past two seasons but is now at No. 2. She won the French Open in June for her fifth major championship and took home a bronze medal at the Paris Olympics in early August.

TMZ is the drug at the center of the case involving 23 Chinese swimmers who remained eligible despite testing positive for performance enhancers in 2021.

Swiatek formally admitted the anti-doping rule violation on Wednesday and accepted her penalty.

She already was provisionally suspended from Sept. 22 to Oct. 4, missing three tournaments during the post-U.S. Open hard-court swing in Asia — the Korea Open, the China Open and the Wuhan Open.