Mos Def has recently joined the cast of the highly anticipated biopic Cadillac Records. According to Variety, Gabriel Union will join the rapper-turned-actor in the Darnell Martin directed project.

Def will play rocker Chuck Berry in this high profile drama, while Union is set to play Muddy Waters' girlfriend Geneva Wade. Also starring in the film are Adrien Brody, Beyonce Knowles and Jeffrey Wright.

The Sony BMG film is expected to be released sometime in 2009.