You learn something new every day! Kris Jenner has been on friendly terms with her ex Caitlyn Jenner since the pair finalized their divorce in December 2014.

But on the Sunday, April 17, episode of I Am Cait, the Kardashian-Jenner matriarch seems genuinely stunned — and a little hurt — to learn that Caitlyn has gone through the paperwork to legally change her name from Bruce.

“I gotta tell you, when Kim brought me some of your clothes that you were throwing away, I was so sad because I thought, ‘Wait a minute. I spent 23 years building this fabulous wardrobe,’” Kris, 60, muses in a preview clip for the episode. “Who knew I was buying the wrong s--t?”

Caitlyn, 66, is sympathetic.

“I know. I know,” she says. “For the last four months, five months, I’ve had lawyers and people and everything going through name change. But I finally got my driver’s license.”

At this, the momager’s eyes widen.

“Oh, you did? What does it say, Caitlyn?” she asks.

“Yeah. Caitlyn Marie Jenner,” the former Olympian confirms.

The retired athlete then drops an even bigger bombshell on Kris, explaining that she also had her name changed on her birth certificate. Kris looks shocked at the news.

“That's kind of sad, though,” Kris says before something else dawns on her. “Wait a second. Does this mean that he didn't exist if you changed the birth certificate? Wait, was I ever married? Was I legally married?”

Watch the clip above for the emotional moment! I Am Cait airs Sundays on E! at 9 p.m. ET.

Can't get enough of Us? Sign up now for the Us Weekly newsletter packed with the latest celeb news, hot pics and more!