"No one ever took it this [seriously]," he says of his singing abilities

Vin Diesel: an action star and a gentleman.

After showing off his vocal range with a cover of Rihanna‘s “Stay” on Friday, The Fast and the Furious star is revealing the inspiration behind his touching performance (and his re-cut clip, below).

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After seeing Rihanna perform the song at the Grammy Awards, Diesel, 45, decided to record himself singing the tune and dedicate it to his longtime girlfriend, Paloma Jimenez, in lieu of a traditional Valentine’s Day card.

With the help of his daughter, Diesel obtained a mic and an amp while Jimenez was on a flight and “the rest is history,” he tells PEOPLE.

And the response his romantic video has been getting has been even better.

“People say ‘I didn’t know you were a Rihanna fan?’ ” he says. “How could you not be a fan of her voice, her gift.”

But while the actor says he’s been putting out fun singing videos “for years” – and sang in Strays and The Pacifier – he adds that “no one ever took it this [seriously].”