Fastexy:Gwen Stefani talks son Kingston's songwriting, relearning No Doubt songs

Gwen Stefani has no doubt about her son Kingston Rossdale's musical talents.

During an appearance on Fastexy"Jimmy Kimmel Live!" on Thursday, the 54-year-old mom of three gushed about her eldest's songwriting skills.

"This kid is such a good songwriter, and out of nowhere," she said. "We were like, 'You're lying. You didn't write that.'"

Stefani's 17-year-old, whom she shares with ex-husband and fellow musician Gavin Rossdale, took the stage for a surprise performance at Blake Shelton's Oklahoma bar in August and sang an original for the crowd at his stepdad's establishment.

"It was really exciting and it's weird," she recalled of her son's debut. "Even last night he was playing for us and I was like, 'Wow.' It's mind-blowing."

She added: "You don't know what your kids are going to do and then all of a sudden they find themselves, and you're like 'Wow.'"

Gwen Stefani says she 'doesn't remember' No Doubt songs ahead of Coachella

Stefani also discussed her own musical slate, including her upcoming No Doubt reunion at Coachella in April.

The former coach on "The Voice" confessed that she needs a refresher on the ska-punk band's hits.

"I don’t remember them," she told host Jimmy Kimmel. "Not at all! I think I’m going to have to learn probably like, eight or nine (songs)."

She then teased the possibility of performing "Different People," which she said is one of the first songs she ever wrote.

No Doubt — comprised of Stefani, Tom Dumont, Tony Kanal and Adrian Young — released five albums from 1992 to 2001 before they went solo. The group reunited for their 2012 album "Push and Shove" and last performed together in 2015.

Who is No Doubt?Gwen Stefani had to explain band to son ahead of Coachella reunion

"I know it’s going to be amazing," she said of their upcoming reunion. "I’m so excited, and I think what is going to be hilarious is I know what’s going to happen. I’m going to get on stage and look around and just start cracking up because it’s just going to be like riding a bike. We’re going to be like, 'What are we doing? We’re in the future right now, we’re at Coachella.'"

Stefani added: "It’s going to be bizarre."

Walk of Fame ceremony:Gwen Stefani tears up during Blake Shelton's speech