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Emily Mortimer still regrets flubbing a line the late Broadway icon Elaine Stritch fed her on the set of 30 Rock.

On season 1 of the hit NBC comedy, Mortimer played Phoebe, an art dealer with “Avian Bone Syndrome” who was briefly engaged to Jack Donaghy (Alec Baldwin), and had the pleasure of working with Stritch, who played Donaghy’s mother.

Well, it was a pleasure, until Mortimer couldn’t understand a joke Stritch gave her last-minute.

“I didn’t understand it, it was like American New York colloquialism, and I didn’t know what it was but I was too scared of her by a million miles to say, ‘I don’t know what that joke is,'” Mortimer confesses to PeopleTV’s Couch Surfing host Lola Ogunnaike.

Unfortunately, this only made Stritch more upset. “She was like, ‘Can you not hear the rhythm of it?'” Mortimer finally told Stritch she couldn’t understand the joke, but Stritch insisted she keep trying, “She was like, ‘Just say it as I f—in’ say it!’

Watch Mortimer recount the hilarious incident in the Couch Surfing clip above.