Online video has captured the moment acclaimed rapper Kendrick Lamar had to stop a white fan from repeatedly using the N-word while onstage with him.
The incident occurred at the Hangout Fest in Alabama over the weekend, when the woman came onstage to add her vocals to 2012 hit 'M.A.A.D. City'.
After the fan, who said her name was Delaney, said "n**ger" into the microphone at least four times, Lamar stopped the music.
"Wait, wait, wait, wait, wait," said the Pulitzer Prize winner.
"Am I not cool enough for you? What's up, bro?" said Delaney.
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Lamar said someone else - presumably another white fan brought onstage earlier - "knew the rules", before explaining them to Delaney.
"You gotta bleep one word," Lamar explained.
Delaney then apologised, seeming surprised she had actually said the deeply offensive racial slur, but added that she wanted to rap it the way it was written.
Lamar then allowed her to give it another, less offensive try; but many other fans in the audience were less forgiving and yelled abuse at her.
Lamar is performing in New Zealand in July.