President Donald Trump on Sunday confirmed a Daily Beast report that his niece Mary Trump signed a nondisclosure agreement that prohibits her from publishing her upcoming book about him. The president told Axios that the NDA Mary Trump signed in 2001 prevents her from publishing anything about her relationship with Donald Trump, Maryanne Trump, or Robert Trump following litigation over a dispute about Fred Trump’s estate.

Mary Trump’s book, Too Much and Never Enough: How My Family Created the World’s Most Dangerous Man, is set to be published on July 28. The book is expected to reveal Mary Trump’s role in the New York Times investigation of President Trump’s taxes. The president told Axios that members of his family are dismayed that Mary Trump has written such a book. “I have a brother, Robert, very good guy, and he’s—he’s very angry about it,” the president said. “But she signed a nondisclosure agreement and she’s obviously not honoring it if she writes a book. It’s too bad.”