Winona Ryder was probably the hardest goodbye for Noah Schnapp when Stranger Things wrapped filming.

The cast filmed the fifth and final season of the Netflix series for a year, wrapping production in December 2024, and for Schnapp, 21, who played Ryder’s onscreen son for nearly a decade, it was almost impossible to let go.

“I remember the last day — or her last day — I remember visiting her on set and just like, I couldn’t let her go,” Schnapp tells PEOPLE of saying goodbye to Ryder, 54. “In that trailer, I was just like — I didn’t expect to be so sad that she was done, but she really feels like she became my own mother.”

“It was so hard,” he remembers. “I was like, ‘Please, no. You can’t go, you can’t go.’ It’s different than with the kids — it’s harder to keep in touch with Winona Ryder. So it was like, ‘Oh my God, I’m never going to see her again.’ “

Ryder played Joyce Byers, mom to Schnapp’s Will Byers, who disappeared into the Upside Down in season 1 and kicked off a years-long journey in Hawkins. In season 5, the mother-son duo were brought closer than ever before as Will confided in Joyce and his friends as he came out as gay before their final battle against Vecna.

“It meant the world that I got to spend this last season with her,” Schnapp says of the Heathers star. “She’s one of my favorite scene partners. I adore her.”

“She just teaches me so much and allows me to kind of explore and try new things,” he continues. “She is incredible. I’m so grateful that I got to close it out with her.”

The feeling has always been mutual for Ryder. At the premiere of season 1 in 2016, she told PEOPLE that she “grew very attached” to both Schnapp and Charlie Heaton, who played her older son, Jonathan Byers.

“I’m not a mom, but I grew very attached. I’ll just leave it at that,” she said. “They’re just amazing. They helped me a lot.”

Schnapp was just 11 years old when filming the first season of the show and met Ryder, and he remembered her being “such a protective, motherly figure to me.”

“She went out of her way to be. She was like, ‘I am going to come to school, go through the lines, work through it.’ She would invite me to her trailer, help sit me down, work through emotional scenes and work with me so much,” he said at an Epic Cons event in 2024. “I am so lucky.”

Other than Ryder, Schnapp bonded the most with Millie Bobby Brown while making the series, and he previously told PEOPLE she’s “my best friend for life” and called her “family.”

“We just always feel so comfortable around each other. There’s no forcing anything,” he said. “It’s just been like that since the first day we met in 2015. No matter how much time we spend apart, it’ll always feel like [we’re] just right back to where we were.”

It was particularly special when they got to share the screen. “We never get to work together, so the little moments we do have onscreen, it’s the best day ever,” Schnapp continued.

“It just feels so easy. That’s what’s so important in this job, is to feel comfortable to be vulnerable, and with her, it’s just so much easier,” he said of Brown, 21.

Stranger Things season 5 is now streaming on Netflix.