John Krasinski Cooks Weekly Dinners For Emily Blunt -- All Thanks to Leonardo DiCaprio!

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John Krasinski is not good at guessing ages.

John Krasinski cooks dinner once a week for his wife, Golden Globe winner Emily Blunt, and -- as he revealed on Jimmy Kimmel Live on Monday night -- it's all because he lost a bet over Leonardo DiCaprio.

Apparently Krasinski didn't believe his wife when she told him the Oscar-winning Revenant actor was 41 years old. 

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"I said, 'How dare you! That cherub of a man -- that cherub of a talent -- can't be more than 28,'" the Aloha star said. DiCaprio turns 42 in November.

Blunt suggested a bet to settle things. "She said 'If I'm right, you have to cook for me every Sunday. And if you're right, you get to play Call of Duty once a week.'"

Obviously Krasinski lost. However, when Kimmel pointed out that he was at the actor's house on a recent Sunday and it was Blunt doing the cooking, the 36-year-old actor and director admitted he's not above doing a little Jedi mind trick to get out of the job.

"You know, with the new Star Wars trailer out, I was like, 'I'm not going to cook tonight,'" he said, waving his hand like Obi Wan Kenobi.

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Let's hope the Force isn't too strong with him on that one. With two young daughters -- Hazel, 2, and baby Violet born in June -- as well as a full work schedule including upcoming filming for Mary Poppins Returns -- we're sure Blunt is happy for all the nights off she can get!

But the father of two, who was on Kimmel to promote his new film, The Hollars, may have only himself to blame for Blunt's enthusiasm for his cooking. Krasinski said he tackled making his wife's favorite meal, a British style roast dinner, for Mother's Day -- despite her warnings against it.

"'What are you going to cook?'" Krasinski recalls her asking. When Blunt made a face in response to his answer, he asked what was wrong. "She goes, 'It's really difficult. You should do something else.'"

It all turned out well, though. "I made one mean roast!" he boasted.

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ET caught up with Krasinski at the New York premiere of The Hollars earlier this month, where he dished on the impact that being a father made on the film. "We started shooting the movie when my daughter [Hazel] was 4-and-half-months-old, and I've got to say that, had I shot this five months before, that it would have been a totally different movie," he said.

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