On Wednesday, Vice President Joe Biden stopped by The Late Show, where host Stephen Colbert pressed the Democratic presidential candidate on a series of recent gaffes.

“You want to talk about issues, but a lot of people want to talk about your gaffes,” Colbert said. “In the last few weeks, you confused New Hampshire for Vermont, said that Bobby Kennedy and MLK were assassinated in the late ‘70s, [and] assured us ‘I am not going nuts.’ Follow-up question: Are you going nuts?”

Biden, who has previously described himself as a “gaffe machine,” joked with Colbert in response, saying that he “came on the Jimmy Kimmel show” because he is not losing his mind. However, he later added that while it is “fair to go after a political figure for anything,” his errors along the candidate campaign trail have not been about a “substantive issue.”

“Any gaffe I have made — and I made gaffes, like every politician I know has — have not been about a substantive issue. I’m trying to talk about what other people have done.”

Biden went on to reference a story from last month in which he said he had pinned a Silver Star on a Navy captain for his heroic efforts in Afghanistan, which the Washington Post called a “moving but false war story.” Colbert went on to clarify the gaffes present in the story, saying that “the branch of the military was wrong…and the date was wrong, and the act he was awarded for was wrong, and the medal was wrong, and what position you held at the time.”

“The essence of it is absolutely true,” Biden responded, referring to his intention to honor “the bravery or the sacrifice” of military service members. “I don’t get wrong things like, ‘We should lock kids up in cages at the border.’”

Colbert then turned to a quote from Biden that NPR previously reported in which the 2020 hopeful Democratic nominee said of his gaffes that “the details are irrelevant in terms of decision-making.” On The Late Show, Biden clarified the statement, saying that “those details are irrelevant” because “the point I was making is absolutely accurate.”

“But some details are relevant,” Colbert said. “That’s where the devil lives, is in the details.”

“The devil lives in the details if the details that you’re talking about would affect the outcome of something that’s about the happen, or should happen,” Biden replied. “I made the case that these folks are heroes and we should treat them as that, and we should be thankful to them.”

Biden, whose campaign is headquartered in Philadelphia, also when on to discuss his relationship with Barack Obama following their time in the White House together, and joked that he has asked former First Lady Michelle Obama to be his Vice President, should he win in 2020.