Ben Affleck Reveals Why He's 'Nervous' to Start Filming 'The Last Duel' With Matt Damon (Exclusive)

'The Last Duel' is a long way from 'Good Will Hunting.'

Ben Affleck is currently on a promo tour for his upcoming movie, The Way Back -- and being especially candid about everything from his sobriety to his divorce to Batman -- but it's his next project that fans of Affleck, period pieces and Good Will Hunting will be most intrigued by.

More than 20 years after their Oscar win for Good Will Hunting, Affleck reteamed with Matt Damon to pen the script for The Last Duel, which both actors will star in. (Their first time acting together since 1997.) "I am very excited. Matt started shooting this week. I am going on Saturday or Sunday, I guess, to France!" Affleck told ET's Rachel Smith.

The Last Duel is set in 14th-century France and tells the true-life story of knights Jean de Carrouges and Jacques Le Gris, who partook in the last officially sanctioned duel to the death after the former accused the latter of raping his wife.

"I am a little nervous," Affleck admitted.

"Because I have never done Medieval! It's 1386, so it is like armor and swords and stuff like that," he explained. "But it was a real pleasure working with Matt and Nicole Holofcener, who wrote the script with us. [Matt and I] kept saying, 'Why have we not done this more often?' We just got lucky that our schedules kind of intersected so that we had some free time to share. We got Ridley Scott directing it. And Jodie Comer's in the movie, so that's very exciting, and Adam [Driver]."

Damon previously gave ET some insight into the trio's writing process on The Last Duel, revealing, "It's this really interesting story of perspective, so Ben and I wrote the male perspectives and Nicole wrote the female perspective. I'm looking forward to making it next year."

The Last Duel is slated to open in select theaters on Christmas Day, before expanding in 2021. In the meantime, Affleck can be seen in The Last Thing He Wanted (now streaming on Netflix) and The Way Back, in theaters March 6.