A lawsuit filed Monday in the US District Court for the Northern District of California claims that Uber discriminates against minority drivers through its star rating system.

Uber uses a star rating system for its drivers, through which Uber passengers rate drivers on a scale of one to five after each ride. Uber uses this system to determine what drivers are terminated, and the score needed to remain a driver is set by Uber.

According to the lawsuit, in San Diego, a driver needed to maintain a 4.6 out of 5 star rating to remain a driver. The plaintiff, who is Asian and from Hawaii, was discharged in 2015 after his rating fell below a 4.6. He claimed that, while working for Uber, he noticed that some passengers were racially biased towards him. He claimed that this racial bias affected the scores he received on the star rating system, which led to his termination.

The lawsuit filed Monday was brought under Title VII of the Civil Rights Act of 1964, alleging both disparate impact discrimination and intentional discrimination. The lawsuit claims that Uber’s use of the system is discriminatory and that Uber was aware of the discriminatory impact of the rating system. Allegedly, customer evaluations are “frequently racially biased.”

The lawsuit is seeking class action status on behalf of “all minority Uber drivers across the country” who were terminated because of the star system.