Waymo has revealed to the DMV that, on October 19, one of its autonomous vehicle prototypes had an accident with a motorcylist.

The San Francisco Chronicle reports that the accident happened near Waymo’s headquarters in Mountain View, California and that the human backup driver was in control of the vehicle at the time of the collision.

In its accident report filed with the DMV, Waymo says that its Chrysler Pacifica prototype was driving at 21 mph (33 km/h) in the middle of three lanes when a car in the left lane began to merge into the middle lane. Eager to avoid an accident, the human operator quickly took control of the car, disabling the self-driving systems, and started to move into the right-hand lane.

However, there was a motorcycle traveling at 28 mph (45 km/h) in the right-hand lane and it hit the rear bumper of the Waymo prototype.

Waymo says the accident could have been avoided if the vehicle was left to its own devices.

In software simulations run by the technology company after the accident, Waymo discovered that the vehicle would have slowed down to avoid the car merging from the left, avoiding a collision.

In a blog post discussing the incident, Waymo chief executive John Krafcik said the car had a 360-degree view of its environment the entire time.

“Our self-driving system was simultaneously tracking the position, direction and speed of every object around it,” he wrote. “Crucially, our technology correctly anticipated and predicted the future behavior of both the merging vehicle and the motorcyclist.”