When Austin Mahone first revealed he was working with singer Pia Mia, fans didn't know what they were collaborating on. But, now Mahone has revealed what it is and when it's coming out.

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In late August, Mahone posted a pic with Pia Mia on Instagram teasing they were working together. "We've got something coming! Be ready. @princesspiamia" Today, Pia Mia tweeted that they collaborated on a cover of Craig David's Fill Me In and it will be out on September 19.

He tweeted about the song on Sunday saying he can't wait for fans to hear what they two of them have been working on.

Austin Mahone Reveals How He Wants To 'Challenge' Himself After 2014 Tour, 'I'm In It For The Long Run'

Mahone just finished his summer headlining tour with Fifth Harmony, The Vamps and Shawn Mendes. Despite his busy schedule, he is set to start recording his first full-length album very soon. Mahone will be playing a post-game concert at the end of this month at Citi Field.

After that Mahone will be traveling to Mexico City for a string of shows with openers Fifth Harmony before hitting up Brazil.

Mahone recently spoke up about having a long career with fans all over the world. "Whenever people see me, I'm a young dude and I sing, and I feel like they're just like, 'Oh, there's just another teen pop star. He's going to have a few songs,' " Mahone told USA Today. "But I want to be more than that. I want to grow, I want to challenge myself to be better and to be different. I want people to know I'm in it for the long run, so you better get used to me."

Tags: austin mahone Pia Mia