Justin Bieber Forgets His Lyrics During Surprise Performance With Ariana Grande (Video)

Justin Bieber lost it with Ariana Grande Saturday night in Miami.

Bieber gave Grande fans the surprise of their lives when he appeared on stage and performed with her in Miami Saturday as part of her Honeymoon Tour even though he totally forgot the lyrics to their duet.

Bieber, 21, filled in for The Weeknd during Grande's song "Love Me Harder," and completely blanked on the words before Grande had to jump in and pick up the lyrics for him.

Even though it was a bonus for the crowd, Justin profusely apologized, "So I feel bad, I forgot the words, Ariana," he explained as soon as the song ended. "I've been trying to memorize them backstage for like an hour."

Ariana didn't appear upset and told the Canadian pop star "nobody heard" while pointing to the audience of screaming fans.

Watch full performance below

The two also performed Bieber's hit "As Long As You Love Me" together.

The "Baby" singer shared a photo on Instagram after the show joking about his flub on stage.

"Had fun with u Ariana, even tho I forgot all the words haha," he captioned the photo.

Watch the full performance below