Multiple endings will be filmed for the final episode of Game of Thrones to stop the storyline leaking.
HBO's President of Programming Casey Bloys says even the stars of the show won't know how it ends.
"I know in Game of Thrones, the ending, they're going to shoot multiple versions so that nobody really knows what happens.
"You have to do that on a long show. When you're shooting, people know," he told an audience at a US college.
"So they're going to shoot multiple versions so that there's no real definitive answer until the end."
The seventh season of Game of Thrones was hit by several high-profile leaks.
Hackers released scripts, HBO documents and unbroadcast episodes from other TV shows.
Four people were arrested in India after a pirated episode was uploaded from an online streaming service in Mumbai.
Another instalment was mistakenly released early in Europe, copied and shared online.
The seventh season of Game of Thrones was illegally downloaded "more than a billion times" according to data seen by piracy tracking firm Muso.
Casey Bloys says that as well as keeping the storyline secret, it'll be incredibly hard to keep everyone happy with the ending.
"Finales are tough," he told students at Moravian College in Bethlehem, Pennsylvania.
"If you think about Six Feet Under, well that was a pretty good finale. But if you think about Seinfeld, if you think about The Sopranos, if you think about Breaking Bad - everybody has an opinion about how a show should end.
"The thing that was interesting about The Sopranos was it did make you think.
"In a way everybody got their own version of it. I think he was probably shot, but I don't think David [Chase] has really told anybody what really happened in his mind.
"But I think that's his point. It can be whatever you think it should be as a fan."
It's unclear when the final series of Game of Thrones will air.
The Hollywood Reporter says production on the final six episodes of the show will start in October and will carry on until the middle of 2018.
"Our production people are trying to figure out a timeline for the shoot and how much time the special effects take," says Casey Bloys.
That could mean fans have to wait until 2019 to see the final instalment.