Ozzy Osbourne has filed a lawsuit against Black Sabbath bandmate Tony Iommi, claiming Iommi illegally assumed 100% ownership of the band’s name.

Ozzy is seeking a 50% stake in the “Black Sabbath” trademark as well as royalties Iommi has already earned. The suit suggests it was Osbourne’s “signature lead vocals” that brought Sabbath its “extraordinary success.” The suit uses Sabbath’s decline in popularity post-Ozzy as proof.

This suit follows an $80 million suit Iommi filed against Live Nation last year, claiming the company sold Black Sabbath merchandise despite a deal that expired in 2006.