Kate Middleton’s mom, Carole, doesn’t find Princess Charlotte’s naughty habit hilarious.

On Thursday, the Duke and Duchess of Cambridge stepped out to launch the inaugural King’s Cup regatta to raise awareness of their patronages. Prince William and Middleton surprisingly brought Prince George and Princess Charlotte along.

In a clip shared on social media, Middleton can be seen encouraging her daughter to wave to the crowd. However, Princess Charlotte didn’t comply and instead wagged her tongue which made the crowd laugh hysterically.

While many found Princess Charlotte’s antics hilarious. According to body language expert Judi James, Middleton’s mom wasn’t as impressed.

“It’s known to be cheeky and a little bit naughty but once a parent has laughed in the way Kate does here the child will learn that it amuses adults and will probably continue to do it,” James told Fabulous Digital. “It allows the child to be a little bit shocking but also funny at the same time and that in turn can make them feel a bit more grown-up. Kate’s reaction is hilarious here and probably totally appropriate for the moment, although Grandma Carole looks as though she might be thinking of nipping this playful naughtiness in the bud.”

James explained that tongue-poking runs in the royal family. It wasn’t just Princess Charlotte who did it. Prince Harry was also photographed wagging his tongue when he was a child and even when he’s all grown up. So, she reminded Carole to be careful with her reaction.

“Carole needs to proceed with caution though as she might be on dodgy ground laying down any rules about tongue-poking as one of the royal family’s most avid fan of this pose was Charlotte’s dad William when he was her age,” Judi added.

Aside from Prince Harry, even Queen Elizabeth, Prince Charles and Prince Philip were all photographed sticking their tongue out. Meghan Markle also did the same in various occasions as shown in these photos.

The Cambridges family including Prince William, Middleton and Prince George were also photographed doing the same. So, the habit is not exclusive to Princess Charlotte.

Kate Middleton, Princess Charlotte
Catherine, Duchess of Cambridge and Princess Charlotte of Cambridge view helicopter models H145 and H135 before departing from Hamburg airport on the last day of their official visit to Poland and Germany on July 21, 2017 in Hamburg, Germany. Getty Images/Chris Jackson