Hopper was to make his big-screen debut as lead character Bug in the Wes Craven film, but was forced to pull out after being struck down with glandular fever.
The 17-year-old said: "Wes said he was thinking about pushing the film back but couldn't because of the possible actors' strike. I saw [Thierot's] audition, and he's a talented guy, really flexible, which fulfills the needs of the role."
Denzel Whitaker, Shareeka Epps and Emily Meade will also star in the film, about seven teens haunted by a serial killer who supposedly died 15 years earlier.
Shooting begins in Connecticut this month.
> Review: Jumper