By law, autonomous vehicles aren’t allowed to carry unaccompanied minors in California. Waymo, Alphabet’s self-driving-car company, doesn’t allow kids under 18 to ride alone anywhere outside of metro Phoenix, Arizona. But that hasn’t stopped some time-strapped parents from using their own accounts to transport their kids to school, extracurricular activities, and even social outings. Some have reported that the lack of drivers makes them feel safer.

Waymo is working to crack down on the practice, the company confirmed Friday, after reports of new mid-ride age-verification checks began to float around on social media. The company has “policies in place” to help it identify violations of its terms of service, Waymo spokesperson Chris Bonelli wrote in a statement to WIRED. “We are continuing to refine our system and processes for accuracy over time.” Violating its terms of service can lead to temporary or permanent suspension of an account, Waymo says.

The company uses cameras inside its cars to check that riders aren’t violating its rules. Its privacy policy notes that the company records video inside the vehicle during trips. Waymo says its support workers “may review video under certain circumstances” and, “in more urgent circumstances,” access live video during a trip. The company says it does not use facial recognition or “other biometric identification technologies” to identify individuals.

The news comes a month after several California labor groups, including the California Gig Workers Union, filed a formal complaint with a state regulatory agency, accusing Waymo of violating the terms of its permit to operate in the state by knowingly transporting unaccompanied minors. The matter was assigned to a judge this week. The state is evaluating new rules that could allow solo riders under 18 in driverless cars, perhaps patterned after a program that permits ride-hail companies with human drivers to transport minors in California.

So far, several fresh-faced adults have been caught in the crossfire. On Tuesday, San Francisco machine learning engineer Nicholas Fleischhauer was about five minutes into his Waymo ride when the car connected him to support. A voice came over the line asking Fleischhauer to verify his age. He told the worker the truth: He’s 35. “I had messy and wet hair and a backpack on me,” he says, by way of explaining why he might have been flagged by Waymo’s system. Plus, “people have told me that I look young for my age.” Fleischhauer says he takes Waymo weekly, but this marked the first time he had been asked about his age.

Since last summer, Waymo has allowed parents in the Phoenix area to set up teen accounts for riders ages 14 to 17. The accounts allow the teen riders’ adults to track their real-time locations during their trips. Waymo says a specially trained team of support agents deals with any issues its teen riders might have. Waymo says that “hundreds” of Phoenix families use the service each week.

In Waymo’s other markets across the US, adults are allowed to ride with guests under 18, though children under 8 must be in a secured car or booster seat.

Ethan S. Klein is 23, but his 26th LA Waymo ride on Thursday—plus the music he was listening to—was interrupted by an in-car call from a support agent who asked him, for the first time, to verify his birth date. Klein is an adult, but his first impulse was almost teen-like. “I was a little startled,” he says. “I thought I was in trouble!”