Serena Williams gets drug-tested far more than other tennis players. This time, an anti-doping official showed up at her house.

Serena Williams is trying to enjoy motherhood out of the limelight, but drug testers just won't leave her alone.

A U.S. Anti-Doping Agency officer apparently showed up at the tennis star's Florida home on June 14 for an unannounced drug test, sources tell Deadspin. It would've been Williams' sixth test this year — far more than any other tennis players have faced, per CBS Sports.

Williams earned a No. 25 seed for the upcoming Wimbledon on Wednesday, shattering the precedent of maternity leave stripping women players of a seeding spot. Williams was recovering from a hip injury that pulled her from the French Open and preparing for Wimbledon when the test attempt happened.

The drug tester apparently arrived around 8:30 a.m. to test Williams, Deadspin says. Williams wasn't home, but the official insisted on waiting for her to return. After a confrontation, the official left without administering a test.

American women far above Williams' 183rd world ranking have been tested twice at most this year, as have American men, CBS Sports says. And Williams isn't happy about it. On May 21, she noted on Twitter that she was tested twice in one week — even though at the time, she was ranked 454th in the world:

Williams apparently called Women's Tennis Association CEO Steve Simon to complain about the June 14 test, Deadspin says. Williams has never failed a doping test in her 23-year career, and she'll keep complying with as many tests as needed, her spokeswoman told Deadspin — but she'll also keep questioning this "invasive and targeted" system.