The Croatian tennis player Marin Cilic says he's going to appeal his nine-month doping ban to the Court of Arbitration for Sport.
Cilic tested positive for the banned substance nikethamide at a tournament in Munich in May.
The 24-year-old says he ingested a glucose tablet containing nikethamide.
Cilic says he's used to buying and using that product - but not in France, where the ingredients are slightly different, and hence the positive test.
In a statement, he says he's never knowingly or deliberately taken a banned substance in his life.
The International Tennis Federation said in its ruling that Cilic had "ingested the stimulant inadvertently as a result of taking glucose tablets, and did not intend to enhance his performance in doing so".
The suspension has been backdated to May 1st, allowing Cilic to return to the circuit on January 31st next year.
Cilic hasn't played since withdrawing from his second-round match at Wimbledon in June.
