President Donald Trump, who built his political rise on promoting far-right birther claims against President Barack Obama, does in fact have a joint defense agreement with leading birther conspiracy theorist Jerome Corsi, The Daily Beast has confirmed.

Rudy Giuliani, Trump’s attorney handling special counsel Robert Mueller’s investigation, said in a brief phone interview Wednesday morning that the joint defense agreement that Corsi had earlier claimed existed does actually exist. Giuliani said he confirmed this with Jane Raskin, another member of the Trump legal team, adding that the agreement is a recent development. Giuliani also said he has talked about the agreement and Corsi with President Trump in recent days, and that Trump told him he “vaguely knows” Corsi, but “doesn’t remember the last time they spoke.”

The Trump lawyer added that he knew of Corsi’s work years ago on the “birther stuff.”

Corsi and Trump’s past relationship wasn’t merely a one-off thing. In April 2011, Michael Cohen, then Trump’s personal attorney and notorious fixer, told NBC News that the future president was promised a pre-publication copy of Corsi’s book, Where’s the Birth Certificate? . Cohen said that “Jerome Corsi had reached out to Mr. Trump to explain certain facts that are in his book,” and that the two men had spoken “on a handful of occasions.”

A month later, Trump called out Corsi in a statement to Mother Jones magazine, challenging Corsi’s assertion that Trump had told him that the long-form birth certificate Obama released was a fake. Corsi also claimed Trump said had said he got a computer expert to conclude the certificate was actually computer-generated.

“Is his birth certificate legitimate? I hope it is for the good of the country, but that’s for experts to determine—not me,” Trump said. “I have not read the book written by Jerry Corsi nor did we discuss whether or not the birth certificate was computer generated or in any way fabricated. I merely asked him how his book was doing and wished him good luck.”

During an on-air chat with fellow leading conspiracy theorist (and Trump fan) Alex Jones, Corsi repeatedly vented that Trump had “dropped out” of the birther movement because he got “a big payment” from NBC, as Trump was the host of the reality-TV series Celebrity Apprentice. Corsi and Jones also discussed how it was possible that Trump was a turncoat and had started working secretly with the Obama administration to subvert conservatives and birthers.

Still, that speculation didn’t entirely kill Trump’s desire to share Corsi’s work. About a year later, Trump tweeted, “Weird--why did BarackObama Sr. fail to list @BarackObama as his son in his 1961 INS application?” and linked to Corsi’s WorldNetDaily article titled, “Immigration officers doubted Obama birth story.”

The Daily Caller first reported on Tuesday that Corsi, a former Infowars journalist with a Harvard doctorate, and a prominent birther conspiracist, wrote in an upcoming book about his experience in the crosshairs of the special counsel investigation that he has a joint defense agreement with President Trump. Such an agreement, relatively common in criminal cases with multiple witnesses and defendants being investigated by the same prosecutor, allows witnesses and subjects of an investigation to share information about the case.

“After debating the pros and cons, we had decided that any time we could get the attorney for the president of the United States to offer assistance to us, we needed to say to be thankful and accept,” Corsi writes in the book, titled Silent No More: How I Became a Political Prisoner of Mueller’s ‘Witch Hunt.’

In October, Giuliani told Politico that Team Trump had 32 joint defense agreements with others being investigated by the special counsel’s office. The issue of such deals re-emerged in the Mueller probe this week after the Caller story and a New York Times report that former Trump campaign boss Paul Manafort’s lawyers were still communicating with Trump’s legal team even after Manafort’s conviction and agreement to cooperate with the government.

Corsi, who said this month that he expects to be charged with lying to federal investigators, told CNN that he was offered a plea deal, but has refused to accept the offer.

“They can put me in prison the rest of my life. I am not going to sign a lie,” Corsi told CNN. He was questioned by Mueller about his links to Trump associate and longtime GOP operative Roger Stone, who has been under investigation for his interactions with WikiLeaks. According to draft court documents obtained by NBC News, Corsi sent an email to Stone tipping him off that there would be document “dumps” two months before WikiLeaks released emails stolen from Hillary Clinton’s presidential campaign.

“Word is friend in embassy plans 2 more dumps,” the email reportedly read. “One shortly after I’m back. 2nd in Oct. Impact planned to be very damaging.”