It’s no secret Donald Trump has numerous joint defense agreements in place with a range of witnesses that are part of special counsel Robert Mueller’s investigation into possible links between the Trump presidential campaign and the Russian government.

Trump’s lawyer, Rudy Giuliani, told Politico as much last month, noting that Trump currently maintains 32 such agreements—including with former campaign chairman Paul Manafort, whose violation of his plea agreement this week thrust him back into the spotlight.

But another, more unexpected, individual also has a joint defense agreement with Trump: birther conspiracy theorist Jerome Corsi, an ally of the president’s former adviser Roger Stone. Giuliani confirmed the existence of such an alliance to The Daily Beast on Wednesday, noting that the agreement is relatively recent.

Corsi reportedly alluded to the agreement in an upcoming book. Trump, meanwhile, has claimed he only “vaguely knows” Corsi and “doesn’t remember the last time they spoke.”

Corsi is one of the far-right proponents furthering the so-called birther theory, the erroneous claim that former President Barack Obama was ineligible to be commander in chief because he wasn’t born in the U.S.

Trump was an avowed supporter of the anti-Obama birther movement, using it to help build his political base in his march to the White House.

Corsi has been questioned as part of the ongoing Mueller investigation due to his ties to Roger Stone. NBC News reported that Corsi tipped off Stone to the WikiLeaks Hillary Clinton email dumps. Corsi was reportedly offered a plea deal by Mueller, but told CNN that he refused it, as he is “not going to sign a lie.” He added that he expects to be indicted for lying to investigators, even though he doesn’t believe he willfully misled anyone.