This week, former Uber drivers in the U.K. claimed that the company fired them after claiming they subcontracted out their rides; the drivers refute that and claim that the facial biometrics the company uses is racially biased and flawed.

An investigative report from Wired, reported that 14 of the workers stated they had their contracts terminated after being accused of subcontracting their shifts to other individuals because the selfie facial biometric system in place failed to recognize who they were. But the workers claim they had never subcontracted shifts to anyone.

The Uber facial identification system uses a photo comparison process which allows an individual to take a photo of themselves for biometric comparison with a photo already stored in the company’s database. The check allows for a choice between an automated system and human verification, Uber says, and human review is performed if someone is removed from the platform. Uber uses a biometric software from Microsoft.