Republican presidential nominee Donald Trump on Sunday tweeted that his Democratic opponent, Hillary Clinton, should release her health records, further promoting a conspiracy theory that she is medically unfit to serve as president.

I think that both candidates, Crooked Hillary and myself, should release detailed medical records. I have no problem in doing so! Hillary?

— Donald J. Trump (@realDonaldTrump) August 28, 2016

But Trump, who has repeatedly questioned Clinton’s trustworthiness, still refuses to release his tax returns, which is standard practice for candidates running for elected office.

Trump claims he can’t release them because he is under audit, but the IRS has asserted that “nothing prevents individuals from sharing their own tax information.”

Clinton has released both her tax returns and a detailed medical record.

The former secretary of state’s physician, Dr. Lisa Bardack, wrote a two-page letter about the candidate’s medical history last year, concluding that Clinton is in “excellent physical condition and fit to serve as President of the United States.”

By contrast, the GOP nominee’s physician, Dr. Harold Bornstein, submitted a brief note declaring Trump to be “the healthiest individual ever elected to the presidency.”

On Friday, Bornstein told NBC that he wrote the letter in just five minutes.

“I get rushed and I get anxious when I get rushed, so I try to get four or five lines done as fast as possible,” Bornstein said. “In a rush, I think some of those words didn’t come out exactly the way they were meant.”