A costume designer who accused Robert Knepper of sexual assault is now suing the actor for defamation for claiming she lied when she accused him of misconduct.

Susan Bertram alleged that Knepper assaulted her in 1991 during the filming of Gas Food Lodging. She said she had gone to the actor’s trailer to drop off costumes when he reached under her dress and grabbed her crotch, ripping into her thighs. He pinned her against the wall and said, “I’m going to fuck your brains out.”

Bertram pushed Knepper away and ran out the door.

The actor, best known for his role as Theodore ‘T-Bag’ Bagwell on Fox’s Prison Break, turned to Instagram to deny the allegations, writing that he was “shocked and devastated to be falsely accused of violence against a woman. It’s just not who I am.” Following publication of her account in The Hollywood Reporter, four more women stepped forward to accuse Knepper of misconduct.

The lawsuit says Knepper’s denials amount to defamation.

“The false Knepper statements have interfered with (Bertram’s) ability to find work, have damaged her reputation in the Hollywood and entertainment community, and have caused her great mortification and emotional distress,” the lawsuit claims.

Bertram argues that Knepper’s statements are “false and slanderous” and impugn her character and competence. People who read or heard about his comments would think she was “untrustworthy, deranged, unqualified to work” — harming her professional reputation. She says, in the court filing, that she suffered severe mental anguish as a result.

“(Knepper) acted with malice, oppression, and fraud, and with the wrongful intention of hurting (Bertram),” the suit alleges. She is seeking damages in a jury trial.

A spokesperson for Knepper could not immediately be reached for comment