Former President Donald Trump on Saturday confused the name of his former White House physician just moments after he said that President Joe Biden should take a cognitive test.

The mix-up took place as the former president bragged that he “aced” a cognitive test. Trump also criticized Biden, saying, “I think he should take a cognitive test like I did.”

“I took a cognitive test and I aced it. Doc Ronny — Doc Ronny Johnson,” Trump said, confusing the name of then-White House physician and current congressman Ronny Jackson. “Does everyone know Ronny Johnson, congressman from Texas? He was the White House doctor.”

Trump continued, bragging about getting “every question right” on the cognitive test administered by Jackson, apparently unaware that he had fumbled his former physician’s name.

Trump in 2018 was administered the Montreal Cognitive Assessment under Jackson.

A spokesperson for the Trump campaign did not immediately respond to a request for comment Sunday evening.

The former president has previously mixed up names of prominent officials and politicians. In January, he confused then-GOP rival Nikki Haley with Rep. Nancy Pelosi, D-Calif., when talking about the Jan. 6 attack on the U.S. Capitol. Trump has referred to Hungarian Prime Minister Viktor Orbán as the leader of Turkey, and he has switched Biden’s name with that of former President Barack Obama, which Trump defended, saying it was done “sarcastically.”

Trump, who turned 78 years old on Friday, frequently attempts to paint Biden as mentally incompetent.

The Biden campaign, however, hit back on Saturday, posting a clip of Trump’s mix up on X. The post garnered more than 18,000 likes.

Trump’s and Biden’s ages, 78 and 81, would make either man the oldest president to hold office. Polling indicates that voters, too, are concerned about what the candidates’ ages may mean for their ability to hold office. Voters appear to consider the issue more of a liability for Biden than Trump, according to polling.