Actress Amanda Seyfried is speaking out about the gender gap in Hollywood, where female actresses are often paid less than their male co-stars even when their roles in a movie carry the same weight.

Amanda Seyfried, 29, famous for her roles in “Mamma Mia!”, “Dear John” and “Les Misérables,” revealed to The Sunday Times that it’s rare for a woman in her industry to land a salary that that’s equal to what her male counterpart gets. Seyfried said:

“A few years ago, on one of my big-budget films, I found I was being paid 10 percent of what my male co-star was getting. And we were pretty even in status.”

Seyfried, who says she has a mellow attitude, argues that her behavior might not have worked in her favor and that she might’ve been taken advantage of:

“I think people think that just because I’m easy-going and game to do things I’ll just take as little as they offer. It’s not about how much you get; it’s about how fair it is.”

But it’s not always possible for actresses to demand to be paid more than what they receive. As Seyfried pointed out:

“You have to decide if you’re willing to walk away from something, especially as a woman.”

Seyfried doesn’t name the male actor who made more than her. It could’ve been Hugh Jackman, whom she starred with in “Les Misérables,” or it could’ve been Channing Tatum, who was her onscreen love interest in “Dear John.”

Other examples: one of the leaked emails from the Sony hack earlier this year revealed that Jennifer Lawrence was making less than her male costars in “American Hustle.”

While Charlize Theron’s name did not pop up in the hack, she was able to negotiate a salary raise after the hack that allegedly matched what co-star Chris Hemsworth was getting, which was in the $10 million range, for “The Huntsman.”

Patricia Arquette, like Seyfried, is one of the rare female stars who’s argued publicly for pay equality. Her Oscar speech for her role in the film “Boyhood” earlier this year included the line:

“It’s our time to have wage equality once and for all and equal rights for women in the United States of America!”

The Sony hack revealed one important thing: where there’s transparency in celebrity salaries, it’s easier for female actresses to negotiate a competitive pay rate.