Justin Bieber surprised Ariana Grande's fans by making a surprise appearance at her concert in Los Angeles last night, but her boyfriend, Big Sean, wasn't happy about it.

Grande and Bieber serenaded the crowd with duet renditions to "Love Me Harder," followed by the hits "Where Are U Now" and "As Long as You Love Me."

The two celebrities were having fun on stage and they embraced for a few big hugs in between songs, which Big Sean was apparently jealous about.

During the performance, which Big Sean wasn't at, he tweeted "Wow."

It was initially unclear if Big Sean was talking about Bieber in his first tweet, but he clarified in a second one. 

"This kid is going to learn not to touch my girl like that. Beliebe that," Big Sean tweeted.

Both tweets were deleted within minutes of being posted, reported Hollywood Life.

Between songs, Bieber gave Grande a big hug. At another point in their performance, during "As Long As You Love Me," he called Grande over to him and put his arm around her from behind.

Bieber, however, didn't appear to get Big Sean's threat and tweeted after the concert thanking Grande for having him and saying that he should go on his own tour soon.

Love the stage. Thanks for having me @ArianaGrande and thanks LA. Gotta tour again soon :)

— Justin Bieber (@justinbieber) April 9, 2015

This was the second time Bieber joined Grande on stage during her tour. In March he joined the 21-year-old singer on stage in Miami, where he messed up the lyrics to "Love Me Harder," People reported.

He finally learned the right lyrics for his Los Angeles appearance.