Sen. John McCain appeared to take a swipe at President Trump in an interview that aired Sunday when he called out the “highest income” Americans at the time who found a doctor to say they had a “bone spur” so they could avoid the Vietnam draft.

McCain was interviewed on C-CPAN3, American TV and talked about the war. The interview was wide ranging, but he mentioned the draft.

“We drafted the lowest income level of America and the highest income level found a doctor that would say that they had a bone spur,” McCain said “That is wrong. That is wrong. If we are going to ask every American to serve, every American should serve.”

The New York Times reported last year that Trump received a total of five military deferments during the war. Four were for education and one—in 1968—was the bone spurs in his heels. During that time, the U.S. inducted about 300,000 men into the military.

“I had a doctor that gave me a letter, a very strong letter on the heels,” Trump told the paper.

Trump and McCain have maintained a tense relationship since Trump appeared on the political scene. Trump was widely criticized for his comment in June 2015 when he said McCain was not a war hero.

“He was a war hero because he was captured,” Trump said during the campaign. “I like people who weren’t captured.”

McCain, 81, languished for more than five years as a prisoner of war in Vietnam after his plane was shot down in 1967 during combat. McCain was released in March of 1973.

McCain revealed in a “60 Minutes” interview a few weeks ago that Trump never apologized to him for the comment.