U.S. Sen. Barbara Boxer (D-Calif.) has praised Warner Bros. over its decision to hire veteran producer Denise Di Novi to direct the thriller “Unforgettable.”

The letter, sent Tuesday to Warner Bros. Entertainment CEO Kevin Tsujihara, noted that Boxer and four other female senators sent another note last month to all the major Hollywood studios asking them to respond to a USC study that found that only 4.1% of top-grossing films in the past decade were directed by women.

“When women’s voices are heard, whether in the U.S. Congress or in the film industry, it strengthens our country,” she wrote. “I will continue to follow the issue of women directors and your studio’s efforts to expand diversity at all levels.”

Boxer’s office noted that she has been encouraged by recent reports of films that will have a woman behind the camera, including Disney’s “Queen of Katwe” and sequel to “Frozen,” four films by Universal this year, including “Suffragette” and “By the Sea,” and a new film on the life of Supreme Court Justice Ruth Bader Ginsburg starring Natalie Portman.

Warner Bros. also recently hired Patty Jenkins to replace Michelle MacLaren as “Wonder Woman’s” director.

“While I am encouraged by recent news reports that some major upcoming films will be directed by women, it is clear that much more must be done to ensure that the many exceptional women in this industry get a fair shot in the director’s chair,” Boxer added.