Blake Shelton celebrated his birthday with a concert in Colorado and a big kiss from girlfriend Gwen Stefani.

The country singer turned 40 years old on Saturday. He spent his special day with his fans, band members and Stefani in a concert held in Colorado. Shelton was also taken by surprise when the “Hollaback Girl” crooner gave him a big kiss onstage after a performance during the singer’s Colorado concert, Us Weekly magazine reported.

The sweet moment happened after Stefani sang her hit “Hella Good” song. Once her performance ended, she called out Shelton on stage and grabbed him for an “extended lip lock,” as stated in the report. The fans, who witnessed the kiss moment between the two singers even, gave the Hollywood couple a cheer.

Blake Shelton and Gwen Stefani Blake Shelton and Gwen Stefani embrace after performing "Go Ahead And Break My Heart" at the 2016 Billboard Awards in Las Vegas, Nevada, U.S., May 22, 2016. Photo: Reuters/Mario Anzuoni

Stefani’s unexpected kiss also appears to have flustered Shelton. “What just happened?! I don’t know how I’m going to follow that,” he told the concert crowd after the sweet moment he shared with his girlfriend. However, he also had a big smile on his face after Stefani’s kiss.

Shelton’s girlfriend also helped to raise the excitement level of the concert goers during the Colorado concert with her performance. “The Voice” coach also shared a short clip of the crowd’s reaction on social media. The country singer took to Twitter to upload a video of Stefani rocking the stage while the fans jumped up and down. Shelton captioned the clip, “Soooooo..... This happened last night.. @gwenstefani #educatedme.”

Meanwhile, Stefani helped to make Shelton’s birthday memorable. She even shared several photos and videos of the celebration on Snapshot, according to E!News. Some of the photos also featured Shelton wearing a pair of “Happy Birthday” eyeglasses. The country singer has also been gifted a special wine glass that had caricature images of himself and Stefani on it.

Shelton also celebrated with two cakes. The first was a chocolate cake decorated with balloons, while the other was a cake shaped like an acoustic guitar.