Josh Trank, director of the 2015 reboot of “Fantastic Four,” has revealed that he wanted to cast a Black actress as the superhero Sue Storm, but got “heavy pushback.”

Kate Mara was cast as Sue Storm, a.k.a. the Invisible Woman, one of the founding members of the Fantastic Four along with her brother Johnny Storm, played by Michael B. Jordan. The heroes are typically portrayed as white siblings in the Marvel comics, but the film’s version of Sue was Johnny’s adopted sister.

“There were a lot of controversial conversations that were had behind the scenes on that. I was mostly interested in a Black Sue Storm, a Black Johnny Storm, and a Black Franklin Storm,” Trank said in an interview with Geeks of Color. “But when you’re dealing with a studio on a massive movie like that, everybody wants to keep an open mind to who the big stars are going to be. ‘Maybe it’ll be Margot Robbie,’ or something like that. When it came down to it, I found a lot of pretty heavy pushback on casting a Black woman in that role.”

Trank said he should have abandoned the project when he realized it didn’t align with his values. He’s been open about the behind-the-scenes turmoil surrounding his superhero movie, which he called “the most disastrous professional experience of my life” in an interview with Variety last month.

“When I look back on that, I should have just walked when that realization sort of hit me, and I feel embarrassed about that, that I didn’t just out of principle. Those aren’t the values I stand for in my own life; those weren’t the values then, or ever, for me. I’m somebody who always talks about standing up for what I believe in, even if it means burning my career out. I feel bad that I didn’t take it to the mat with that issue. I feel like I failed in that regard,” he said.

The “Fantastic Four” reboot received mostly negative reviews from critics and fans, and grossed only $56 million in the U.S and $168 million worldwide against an estimated budget of $155 million. It was the lowest grossing “Fantastic Four” movie to date and one of the lowest grossing films based on a Marvel property.

After acquiring 20th Century Fox, Disney now has the rights to the Fantastic Four and plans to introduce them into the Marvel Cinematic Universe in the future. A representative for Disney did not return Variety‘s request for comment.