Jo-Wilfried Tsonga hits a return to Karen Khachanov at the 2019 Citi Open on Tuesday at Rock Creek Park Tennis Center in Washington DC. Photo: IC

While tennis stars donate money to the Australian bushfire crisis through every thunderous ace they serve, Switzerland's Belinda Bencic will cough up on her Achilles heel - double faults.

"Although I'm not the best at hitting aces but much better at hitting double faults, I will donate $200 for every one I serve at my next tournaments," the 22-year-old world number eight tweeted on Wednesday.

"Like that, I won't be angry at myself when I hit one and finally they will be useful," she also said.

Bencic is on her way to Australia where she will play next week at Adelaide before eyeing the season-opening Grand Slam event at the Australian Open in Melbourne later this month.

Last season, Bencic committed 322 double faults on tour and served 204 aces.

Current world number one Ashleigh Barty fired 409 aces and 201 double faults while the corresponding figures for 23-time major winner Serena Williams were 206 and 80.