When you’re making a show set in the 1980s and jam-packed with all things 1980s pop culture, it helps to have a 1980s icon on set. Such is the case for “Stranger Things” and Winona Ryder, who not only stars in the series as Joyce Byers but also makes sure creators Matt and Ross Duffer maintain 1980s accuracy on set. Ryder’s co-star told Harper’s Bazaar (via IndieWire) that the Duffer Brothers have often had to change scripts after Ryder fact-checked them.

“She’d tell them, ‘This song actually came out in ’85, and you have it in ’83,’” David Harbour said. “She knew all of these minute, tiny details they didn’t even know, and they had to change things in the script based on that…It’s just kind of epic how wild her mind is and how it goes to all these different corners.”

Ryder had her film debut in 1986 in the movie “Lucas.” Her career skyrocketed in the late 1980s with Tim Burton’s “Beetlejuice,” the cult classic “Heathers” and the Jerry Lee Lewis biopic “Great Balls of Fire.”

Ryder also serves as a mentor on set to the show’s ensemble of teen actors. “I want the kids to understand, this does not happen,” the actor said. “This is really unusual. And I’m always telling them, ‘The work is the reward!’ Because when I was that age, it was so hard to enjoy the fruits of my labor.”

“This business is brutal,” Ryder continued. “You’re working constantly, but if you want to take a break, they tell you, ‘If you slow down, it’s going to stop.’ And then it did slow down. So then you’re hearing, ‘It’s going to be impossible to come back.’ And then that changes to, ‘You’re not even part of the conversation.’ Like, it was brutal.”

According to Ross Duffer, Ryder’s mentorship has been essential for the show’s breakout teen Millie Bobby Brown.

“[Winona has] talked to the kids about what celebrity is like and how the press can be and the anxiety and confusion that comes along with celebrity,” Duffer said. “I think she’s really helped them. I know she’s specifically helped Millie [Bobby Brown] a lot to work through that. And that’s something that no one else can help with, really, because so few people have experienced it. It’s not something I understand. It’s not something that, you know, even a parent would understand.”

The first seven episodes of “Stranger Things” Season 4 are now streaming on Netflix. The final two installments of the series launch July 1.