Diane Lane is doing her best not to swoon over Matthew McConaughey after he named her his first celebrity crush!

The "Serenity" co-stars spoke with ET on Wednesday at the New York City premiere of their mysterious new thriller, and McConaughey admitted to being a little sweet on Lane back in the day.

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“I had a crush on her since a film she was in -- 'Lonesome Dove,'” the 49-year-old actor confesses. “That may have been almost preteens for me, so [now] I get to work with her. She looks about the same as she did back then. And she’s one of our great actor-actresses that we have in show business, in the business of storytelling. It was a privilege I got to work with her.”

McConaughey was so excited, in fact, he told Lane of his childhood crush during their first day on set.

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“I think I blocked it out,” Lane, 54, says of McConaughey approaching her on set. "I don’t think he lied. I think he did say that to me day one, and I just had, like, white out. I couldn’t cope. I said, ‘I’m gonna stay in character. Thank you for the compliment. I am dying. Love you too, babe.’”

As for her co-star gushing over her youthful looks, Lane is thrilled by the sentiment.

"I’m dying. I don’t know what to say about that. I mean, I want to live up to that,” she muses. “I had a blast working with Matthew, and it’s about time that we got to work together after all these years, so I’m so happy.”

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The pair had to act professional from the start since they filmed their love scenes first. "Of course you must start with the love scenes. I mean, that’s what the cinema gods do,” Lane quips. "Hello, nice to meet you finally. Let’s get to it!"