Taylor Swift gives a surprise performance at the couple's commitment party

Taylor Swift just made the big day of a couple even sweeter!

After a fan named Alex Goldschmidt proposed to his boyfriend Ross Girard, the 29-year-old pop star gave a surprise performance at their engagement party.

According to Swift, Goldschmidt sent him an email to inform him of his plans. He also mentioned that his hit "King of My Heart" was special for the duo. Swift therefore agreed to attend the engagement party at the Sycamore Tavern in Los Angeles and surprise Goldschmidt's fiancé with a sweet serenade.

Of course, the family and friends of the couple were completely shocked to see the winner of the 10 Grammy come out with her guitar.

"I have not been on tour for a while, but I hope it will always go," she said before playing the number.

Swift interpreted the song in a blue dress with a white print.

"It comes from Alex, but sung by me," she told Girard.

Needless to say, both were really touched by Swift's sweet gesture.

"I decided to propose to Ross to listen to this song in my car," wrote Goldschmidt on Instagram. "I can not thank Taylor enough for wanting to help make this day so special."

Watch the video to see the surprise.