When Kacey Musgraves met the UK's Prince Harry on Friday (Nov. 13) at the Royal Variety Performance at Royal Albert Hall, she didn't know the rules.

She said so on her Instagram, when she posted a picture of the two of them high-fiving one another.

"When Texas meets Royalty. #casual #highfives #idontknowtherules," she captioned the picture with Prince Henry Charles Albert David of Wales.

But as long as she called him "Your Royal Highness" and addressed him as "Sir," she did just fine on the rules.

According to the Royals' official website, a small curtsy from a woman is the traditional greeting, but it is not necessary.

And if Musgraves' song is true, and she ain't "Pageant Material," then I think her royal high five was a win for country music.