US President Donald Trump has long claimed to have an original Renoir painting.
However, art experts from Art Institute of Chicago have insisted he is wrong, because the actual work is in their gallery.
Trump's biographer Tim O'Brien told Vanity Fair he challenged the real estate tycoon several years ago after spotting the copy in the latter's private jet.
Pointing out the picture hanging in the jet, Trump boasted: "You know, that's an original Renoir."
O'Brien grew up in Chicago and knew the original well, which has hung in the Chicago museum since 1933.
However, O'Brien replied: "Donald, it's not. I grew up in Chicago, that Renoir is called Two Sisters on the Terrace, and it's hanging on a wall at the Art Institute of Chicago."
The following day, Trump appeared to have forgotten the previous day's conversation, and declared: "You know, that's an original Renoir."
After Trump sold the private jet, the painting ended up in Trump Tower in New York and featured in the background of a Fox News interview with his wife Melania last year.
O'Brien said: "I'm sure he's still telling people who come into the apartment, 'It's an original, it's an original.'
"He believes his own lies in a way that lasts for decades. He'll tell the same stories time and time again, regardless of whether or not facts are right in front of his face."
Art Institute spokeswoman Amanda Hicks has come forward to support O'Brien, stipulating the institute is "satisfied that our version is real".