Some itches just shouldn't be scratched.

Jennifer Lawrence learned that the hard way. The Passengers star revealed on The Graham Norton Show that she once almost killed her sound guy -- by scratching her butt.

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"We were filming in Hawaii, and there were sacred rocks," the 26-year-old actress shared. "You're not supposed to sit on them."

"I however, was in a wetsuit... Oh, my god they were so good for butt itching," Lawrence added, which is precisely the moment everything went wrong.

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"One rock ... ended up coming loose," she explained. "It was a giant boulder, it rolled down this mountain, and almost killed our sound guy."

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Thankfully, everyone is OK!

Meanwhile, Lawrence's "Passengers" co-star, Chris Pratt, has been doing a bit on Instagram lately, where he shares pics of himself with Lawrence cropped out of them.

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"The Graham Norton Show" airs on Saturday, Dec. 10 at 10 p.m. ET/PT on BBC America.