Five members of the U.S. women’s national soccer team, including stars Carli Lloyd, Hope Solo and Alex Morgan, filed a complaint at the Equal Employment Opportunity Commission against the U.S. Soccer Federation alleging that they are paid almost four times less than the men’s national soccer team, despite generating nearly $20 million more in revenue in 2015. The complaint alleges that U.S. Soccer violated the Equal Pay Act by paying the reigning World Cup champions significantly less than the U.S. men’s team for similar work.

The complaint, which was filed on behalf of the entire USWNT, compares the bonuses, appearance fees and per diems for the women’s team and men’s team, noting that the men’s team players receive $5,000 for a loss in a friendly match – and as much as $17,625 for a win – while the women’s team players receive $1,350 for a win in a similar match and receive no bonus for losses or ties. The women’s and men’s teams have the same work requirements, though, according to the USWNT’s attorneys, with an equal number of minimum friendlies in which they must play and the same requirements to prepare for their respective World Cups.

The complaint alleges that there is no legitimate, non-discriminatory reason for the pay gap and points to minutes from the Federation’s annual general meeting held earlier this year, which show that U.S. Soccer expects the women’s international games to bring in more revenue than the men’s games this year, and significantly more in 2017. The women’s team is also more successful on the field than the men’s team, having won three World Cups and four Olympic gold medals in the last 25 years. The complaint requests that the EEOC conduct an independent investigation and seek relief on behalf of the women’s team.

The filing comes on the heels of another legal battle between the USWNT and U.S. Soccer over the terms of their collective bargaining agreement, which expired in 2012. U.S. Soccer filed a lawsuit in federal court last month seeking a declaratory judgment that its contract with the union that represents the U.S. women’s team runs through December 31, 2016. The union maintains the memorandum of understanding agreed to in March 2013 which extended the collective bargaining agreement can be terminated at any time.

The EEOC will conduct an investigation of the women’s team’s claims and determine if U.S. Soccer violated federal non-discrimination laws. In the meantime, the USWNT will continue preparing for the 2016 Summer Olympics in Brazil where they will defend their 2012 gold medal.