Google-parent Alphabet is on the verge of launching a service with its self-driving cars that could rival Uber and Lyft, The Information reported on Tuesday.

But Waymo, Alphabet’s self-driving car company, must fix a glitch first, according to The Information: The vans have trouble making left turns.

The Chrysler vans, which would pick up and drop off passengers in Arizona, would be ideally monitored remotely, rather than with a “safety” driver, The Information reported. But the software in the cars reportedly gets tripped up by certain safety issues, especially when there is no green arrow for left turns.

To be sure, the cars are still being tested and improved: Waymo recently released a detailed blog post about how it is using simulations to quickly train its cars to learn tricky turns.

“At the corner of South Longmore Street and West Southern Avenue in Mesa, Arizona, there’s a flashing yellow arrow that permits cars to turn left,” Waymo wrote in the post. “Navigating this type of intersection can be tricky for humans and self-driving cars alike — drivers must carefully move into a five-lane intersection and then find a gap in oncoming traffic. Turning left too soon may cause a driving hazard for oncoming traffic; making the move too late may mean frustrated drivers behind.”

Still, a glitch could be one of the few setbacks that is keeping Waymo from leapfrogging ride-sharing services like Uber and Lyft, given data that indicates that Waymo is the leader in autonomous driving technology. The ride-hailing pilot in Arizona could help Waymo log more miles on the road, which could be valuable in helping the company keep its lead.

Though Alphabet is an investor in Uber and may do the same with Lyft, the search giant clearly has ambitions in the transportation space itself. Google’s Waze has already launched a carpool service, and Waymo continues to hammer Uber in court over allegations of stolen trade secrets.

Even as Waymo litigates one type of self-driving technology with Uber, it has developed ideas for others, according to patent applications published on Tuesday. Lyft was not immediately available to comment. Uber declined to comment.

For more on the left-turn issue, see the report in The Information.