She's fought and kissed on screen as Katniss Everdeen in the "Hunger Games" film franchise, but there's one thing Jennifer Lawrence had to do in "The Hunger Games: Mockingjay - Part 1" that absolutely terrified her: sing.

In "Mockingjay," Katniss is caught on camera singing "The Hanging Tree," a song her father taught her. Her a cappella rendition is really spooky and pretty, and the song (with lyrics adapted from Suzanne Collins' novel) becomes a sort of rallying cry for the rebels of Panem, sung by their Mockingjay.

For Lawrence, however, singing the song on camera was not the transcendent act that it's portrayed as on film.

"I've never sung in front of people or anyone and I don't like that, so that was a terrible day," Lawrence told MTV News at the London press day for "Mockingjay."

Her co-stars, Josh Hutcherson and Liam Hemsworth, rushed to reassure her.

"You have a cool voice, Jen, just saying," Hutcherson said. "A cool voice."

Hemsworth, for his part, remembered Lawrence being in a hurry to get the scene over with.

"[Director] Francis [Lawrence] and I were trying to tell her after the first take that she did a great job, but she just told us to shut up," he said. "'Shut up, don't talk to me for the rest of the day. Let me just do this, and we'll never speak of it again.'"

"The Hunger Games: Mockingjay - Part 1" hits theaters November 21.