Dj Mustard is facing further legal action from his producer pal Mike Free amid allegations he is owed royalties for 20 of the hip-hop star's biggest hits.

Free, real name Mikely Adam, originally filed suit against his childhood friend in December (14), claiming he has not been properly credited for his contributions to eight of Mustard's creations, such as Tyga's Rack City, 2 Chainz's I'm Different and Big Sean's I Don't F**k With You.

He has since amended the lawsuit to include 12 other tunes, like Chris Brown and Tyga's Banjo and Kid Ink and Dej Loaf's Be Real, reports Billboard.com.

Free's lawyer, intellectual property attorney Robert Allen, says, "Mike is a real class guy. All he's looking for is to be properly credited and paid for the things that he did. He doesn't have any ill will toward Mustard. No bad blood. It's just about the work that he did in creating these songs, and the masters, and being properly credited and compensated."

DJ Mustard, real name Dijon McFarlane, has yet to comment on the allegations.