Sienna Miller is opening up about Chadwick Boseman’s “unfathomable” act of generosity from when they worked together on “21 Bridges.”

In an interview with Empire published on Monday, the actress revealed that Boseman, who passed away last month after a private battle with colon cancer, gave a portion of his “21 Bridges” salary to her to ensure that she was compensated fairly and received the pay she “deserved.”

“He produced 21 Bridges, and had been really active in trying to get me to do it,” began Miller, 39. “He was a fan of my work, which was thrilling, because it was reciprocated from me to him, tenfold. So he approached me to do it, he offered me this film, and it was at a time when I really didn’t want to work anymore. I’d been working non-stop and I was exhausted, but then I wanted to work with him.”

Miller said she was initially “hesitant” to join the project and told the studio she would only agree to star in the film on the condition that she would be “compensated in the right way.” When the studio turned her down, Miller said Boseman stepped in.

“I didn’t know whether or not to tell this story, and I haven’t yet. But I am going to tell it, because I think it’s a testament to who he was,” explained Miller, who played Detective Frankie Burns in the cop thriller. “This was a pretty big budget film, and I know that everybody understands about the pay disparity in Hollywood, but I asked for a number that the studio wouldn’t get to. And because I was hesitant to go back to work and my daughter was starting school and it was an inconvenient time, I said, ‘I’ll do it if I’m compensated in the right way.'”

“And Chadwick ended up donating some of his salary to get me to the number that I had asked for,” she continued. “He said that that was what I deserved to be paid.”

Miller described Boseman’s gesture as “the most astounding thing that I’ve experienced.”

“That kind of thing just doesn’t happen,” she expressed. “He said, ‘You’re getting paid what you deserve, and what you’re worth.’ It’s just unfathomable to imagine another man in that town behaving that graciously or respectfully. In the aftermath of this I’ve told other male actor friends of mine that story and they all go very very quiet and go home and probably have to sit and think about things for a while. But there was no showiness, it was, ‘Of course I’ll get you to that number, because that’s what you should be paid.'”

Miller’s interview came exactly one month since Boseman’s passing. The “Black Panther” star died on August 28 at the age of 43 following a four-year battle with colon cancer.

His death was confirmed via a statement on his social media pages.

“It is with immeasurable grief that we confirm the passing of Chadwick Boseman,” began the statement.⁣ “Chadwick was diagnosed with stage III colon cancer in 2016, and battled with it these last 4 years as it progressed to stage IV.”

“A true fighter, Chadwick persevered through it all, and brought you many of the films you have come to love so much,” it continued. “From Marshall to Da 5 Bloods, August Wilson’s Ma Rainey’s Black Bottom and several more, all were filmed during and between countless surgeries and chemotherapy.”

“It was the honor of his career to bring King T’Challa to life in Black Panther. ⁣He died in his home, with his wife and family by his side. The family thanks you for your love and prayers, and asks that you continue to respect their privacy during this difficult time.”