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Blake Shelton wishes Gwen Stefani happy birthday: 'I love you so much it's stupid'

Another year, another sweet birthday message between the lovebirds.
STX Films World Premiere Of "UglyDolls" - Arrivals
LOS ANGELES, CALIFORNIA - APRIL 27: Gwen Stefani and Blake Shelton arrive at the STX Films World Premiere Of "UglyDolls" at Regal Cinemas L.A. Live on April 27, 2019 in Los Angeles, California. (Photo by Steve Granitz/WireImage)Steve Granitz / WireImage
/ Source: TODAY

Thursday marked a milestone birthday for Gwen Stefani — the music star and coach of "The Voice" turned 50 years old!

And her beau of four years, Blake Shelton, made sure the whole world heard his offbeat expression of love on her big day.

"Happy Birthday @gwenstefani!!!!" he wrote on Twitter. "I love you so much it's actually stupid... And possibly illegal in the state of California."

OK, we won't ask!

Stefani and Shelton have been dating since 2015, after meeting on "The Voice," and have been charming the public with their displays of affection on social media ever since — especially on their birthdays.

In 2016, Stefani memorably shared some of her love's childhood photos to ring in Shelton's 40th birthday. The next year, she presented him with an armadillo cake.

STX Films World Premiere Of "UglyDolls" - Arrivals
Stefani with her sons and Shelton in Los Angeles in April. Stefani told TODAY in September that Shelton is a great dad to her boys. Steve Granitz / WireImage

Later that year Shelton gave Stefani a sweet birthday shout-out on Twitter: "Happy Birthday @gwenstefani!!! Why don't you go ahead and NEVER break my heart!!!!"

"Thank u for saving my life," Stefani replied, proving that the two are both head over heels for each other.

Last year's Twitter shout-out from Shelton was a little more PG-13-rated, while Stefani made sure to fly her flag high on his big day.

This year, she hasn't replied back yet, but we're all waiting with anticipation. Whenever these two celebrate, it's almost like we're all invited to the party!

Stefani stopped by TODAY in September to talk about her return to "The Voice" — and to dish on her relationship. She said Shelton is a great dad to her three boys.

"He's been helping out a lot, so I literally get to the point where I'm like, 'You gotta get home, I need help,'" she said.

Stefani also said she's just as surprised as everyone else that they ended up together.

"Something I never thought that would happen to me, that I would be with someone that actually had a mullet," she said, referencing a throwback photo of Shelton rocking the unique hairdo. "Life is full of surprises."