Wal-Mart has appealed the 9th Circuit Court of Appeals’s ruling that a class action gender discrimination lawsuit filed against Wal-Mart can move forward to trial. The case will now go to the U.S. Supreme Court. In April, the 9th Circuit Court ruled that more than one million current and former female employees of Wal-Mart can sue the corporation as a class. The suit, Wal-Mart Stores v. Dukes, is the largest employment class action in history, according to the National Law Journal. The lawsuit was initially filed in 2001 by Betty Dukes, a former Wal-Mart employee, and six other plaintiffs who worked in 13 of Wal-Mart’s 3,400 US stores. The women are seeking punitive damages and back pay for gendered wage discrepancies for all female employees of Wal-Mart since 1998, according to USA Today. The plaintiffs claim that men earn systematically higher wages and receive more frequent promotions at Wal-Mart, regardless of women’s competitive quality of work and seniority. The current appeal does not dispute the merits of the gender discrimination claim. Wal-Mart has asked the court to throw out the case because it claims that women certified as a class in the case “have little in common but their sex and this lawsuit”, according to the National Law Journal. The lawsuit could cost the company billions if it loses, USA Today reports. The Supreme Court is expected to decide whether it will hear the case in the fall.