Ashton Kutcher Is 'So Pissed' at Laura Prepon for Not Telling Him She Was Engaged -- Watch!

The 'That '70s Show' co-stars go way back... but he had to find out through the news!

Ashton Kutcher is not too pleased with Laura Prepon!

The That '70s Show star guest co-hosted Friday's Live With Kelly, where he expressed his frustration over the fact that his former co-star did not personally share with him that she had gotten engaged to Ben Foster, and had to learn about it just like everybody else.

"I'm very upset with her right now. She just announced this engagement, and I had to find out in the news! She's my friend," the 38-year-old actor explained to Kelly Ripa. "By the way, it's not just a random engagement. It's an engagement to another friend of mine!"

WATCH: Laura Prepon Engaged to Ben Foster -- See the Flawless Ring!

Now, it's possible that Prepon held her tongue as payback for Kutcher not telling her he was engaged to Mila Kunis right away.

"When Mila and I got engaged, Pre was like, 'What? This is crazy! You guys, it was like 20 years ago. You were friends and no one saw this coming, and now you're engaged and I have to find out this way,'" Kutcher shared.

But when Kutcher confronted his old friend about it on the show, she had the most hilarious response.

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"I've been in prison! I have limited communication with people!" said Prepon, referencing her role on Orange Is the New Black.

Watch the animated exchange between old friends below.

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ET caught up with Prepon -- who was rocking a shiny new diamond ring on THAT finger -- at the NYC premiere of The Girl on the Train. And while she didn't speak about her engagement, Prepon did comment on the supportiveness of her friends when it comes to her new movie.

"All my friends are so supportive and amazing," she said about their excitement to see The Girl on the Train finally hit the big screen. "They're supportive of anything I do."

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Meanwhile, Kutcher recently broke some big news of his own, that he and his wife are expecting a little boy!

Watch the video below.