HBO's Perry Mason remake is making a change behind the scenes.

Writers Rolin Jones and Ron Fitzgerald have signed on to pen the Robert Downey Jr. drama currently in development, The Hollywood Reporter has confirmed.

The duo are stepping in for True Detective creator Nic Pizzolatto, who was originally attached to write when news first broke about the project a year ago. However, Pizzolatto has since become pre-occupied with the third season of True Detective.

While not officially ordered yet at HBO, Oscar winner Mahershala Ali has officially signed on for the third season of the anthology series.

"I've read five scripts on the new season and I think they're terrific," HBO programming president Casey Bloys told reporters in August at the Television Critics Association summer press tour about season three. "When we find a director, we'll be a go on that."

Jones and Fitzgerald have worked together several times before, writing for Weeds, Friday Night Lights and United States of Tara. Jones' other credits include another HBO drama, Boardwalk Empire, and The Exorcist. Fitzgerald has also written for NBC's Prime Suspect remake and Last Resort.

In addition to starring, Downey is attached to exec produce the project with his wife and producing partner Susan Downey. The Iron Man star was originally attached to a film remake of Perry Mason at Warner Bros. several years but the project was never made.

Created by Erle Stanley Gardner, Perry Mason is a Los Angeles defense attorney and served as the inspiration for the CBS series of the same name. The drama ran from 1957 to 1966 and starred Raymond Burr in the title role.