Two new cast additions to upcoming horror sequel "It: Chapter 2" are making it clear that the flick -- like its predecessor -- is sticking closely to author Stephen King's source material.

Deadline reports that actor-director Xavier Dolan and actor Will Beinbrink ("Free State of Jones," "I Saw the Light") have just joined the cast of the film, which officially began production earlier this week. Dolan will be playing Adrian Mellon, while Beinbrink will portray Tom Rogan.

Both characters are key supporting players in King's sprawling novel, and as Slash Film notes, their additions to the "Chapter 2" cast make it clear that this isn't the '90s TV miniseries version of events. Here's some background on the two men, via Slash Film:

In Stephen King's novel, Adrian Mellon is a young gay man living in Derry, Maine – home of Pennywise the Clown. In the present-day section of the book, a group of homophobic bullies attack Mellon and his boyfriend, Don Hagarty. The attackers throw Mellon over the side of a bridge into the canal, at which point he's attacked by Pennywise. This act triggers Pennywise's return to Derry after decades of dormancy.

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In King's novel, Tom is Bev's abusive husband. She flees from him to return back to Derry, and he comes after her. These two bits of casting both indicate that It: Chapter 2 is going to further distance itself rom the 1990 miniseries adaptation of King's novel. In that take on the material, Adrian Mellon didn't appear at all. And while Tom Rogan was a character, he was featured only briefly in one scene.

Also an interesting note about Dolan's casting: He's good friends with Jessica Chastain (who's playing grown-up Beverly in the sequel), and even cast her in his upcoming flick, "The Death and Life of John F. Donovan," though he ended up cutting her character during the editing process. Apparently the pair is still on good terms, though, and now, they'll get to work together again. (Though not, as Slash Film points out, in any scenes together -- at least as written in the book version of events.)

"It: Chapter 2" also stars James McAvoy, Bill Hader, James Ransone, Andy Bean, Jay Ryan, and Bill Skarsgård. It's due in theaters on September 6, 2019.

[via: Deadline, h/t Slash Film]