Even celebrities have bad hair days.

And that’s just what happened to Angelina Jolie on Sunday, when she walked the red carpet at the Rome Film Festival premiere of “Eternals” sporting choppy, uneven extensions that shocked her fans on social media.

“Now, I’m no hairdresser but whoever did Angelina Jolie’s hair extensions did it wrong and/or drunk,” one person tweeted, while another simply quipped, “somebody getting fired.”

But how could one of the world’s most famous women have suffered such a major mane mishap?

According to celebrity extension expert Priscilla Valles — who’s lengthened the locks of A-listers including Hailey Baldwin, Christina Aguilera, Megan Fox and the entire Kardashian-Jenner crew — Jolie’s beauty blunder stemmed from improper extension density and placement.

Fans were horrified over Angie’s red carpet hair malfunction.

“What went wrong with this look is that there are not enough extensions, and they are not high up,” Valles told Page Six Style, adding that correct installation involves “first putting [extensions] on top, and then building them up and making sure there is enough in so you don’t see a demarcation line, which you see clear as day with Angelina.”

A quick trim can also help seamlessly blend extensions in with the wearer’s real hair, resulting in a look that’s luxuriously long without being lopsided.

“If someone has a really blunt cut, use thinning shears to barely hit the ends to break up that line — or hold the hair up to chip in some layers to get rid of the blunt end,” Valles said. “The thinner the ends are, the better the hair blends together.”

Megan Fox, Kim Kardashian and Christina Aguilera show off hair extension expert Priscilla Valles’ handiwork.Instagram

Another extension error she spies often? A bad shade match.

“Even if you have the right amount of extensions in and build them properly, the color being off ruins the entire look,” Valles said. “The ends should always be half a shade lighter, the way hair would naturally be from root to end.”

Angelina Jolie walked the “Eternals” red carpet in Rome with choppy, uneven hair extensions that caused quite the social media commotion.Mondadori Portfolio via Getty Im

The star stylist recently launched her own line with Glam Seamless, one of the industry’s top hair extension brands, along with virtual courses to help customers and pros alike avoid these common mistakes. Her line also happens to include more hair per pack than any other on the market.

“Whether you have thin hair or a blunt haircut, you will not run out of extensions,” she promised. “Having enough for a full head is key!”

Hollywood’s most sought-after extensionist, Priscilla Valles recently launched her own line with Glam Seamless.