Scarlett Johansson jokes that her prenup required Colin Jost to cameo in Fly Me to the Moon

Scarlett Johansson just taught Colin Jost an important lesson about reading the fine print.

Stopping by The Tonight Show on Monday, the actress told host Jimmy Fallon how her husband came to cameo in her latest film, Fly Me to the Moon: It was less of a request and more of a contractual obligation, Johansson joked.

"Greg Berlanti, who was our director, is a huge fan of Colin's," the Black Widow and Lost in Translation star explained. "And Colin, I think he had to do it because it's, like, in our prenuptial agreement. If I ask him to do something, he has to be there to support me."

As Fallon laughed, she added, "He has to be in every one of my films."

Johansson and Jost, who were first linked in May 2017, have been married since October 2020. They welcomed their first child together, son Cosmo, the following summer. Johansson also has a daughter, Rose Dorothy, 9, from her prior marriage to Romain Dauriac.

Guaranteed cameos aren't the only benefit of being married to a fellow performer. Johansson went on to reveal another perk of their relationship: She always has a partner to run lines with. Unfortunately, enlisting Jost to help her learn lines doesn't always go the way she hopes it will. 

"I run lines with him, which is great," she told Fallon. "You'd think that would be very convenient because you have a partner there to help you out. You learn your lines for tomorrow or whatever."

The issue? "He does, like, real serious… He really commits to the line reading," Johansson said. "And it's not always the performance I want it to be."

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"Yeah, you don't want any performance," Fallon pointed out. "Just read the lines, you're not going for the Oscar here."

Johansson agreed: "I'm just like, 'Say the lines!' Exactly!" Instead, Jost offers "big dramatic pauses" and "gets really into it," to which his wife responds, "'I can't focus. Forget it. I'll just learn them myself.'"

Jokes about Jost's line reading skills aside, Johansson went on to praise her husband's performance in their upcoming movie, noting, "He's great. He's so funny and off-the-cuff and charming and great."

Fly Me to the Moon arrives in theaters July 12. Watch Johansson discuss the film and her husband’s cameo in the video above.