Autonomous trucking company TuSimple used its second-quarter earnings call to address an April crash during which one of the company’s autonomous trucks suddenly veered across the I-10 highway in Tuscon, slamming into a concrete barricade.

The crash first came to light via a YouTube video that showed footage of the crash along with a letter from the Federal Motor Carrier Safety Administration (FMCSA), dated May 26, alerting TuSimple to a “safety compliance investigation.” The accident was later reported on by The Wall Street Journal.

“An error occurred when a test driver and safety engineer tried to reenter autonomous driving mode before the system computer was primed to do so, and the truck swerved, making contact with the highway barrier,” said Xiaodi Hou, TuSimple co-founder and CEO, during Tuesday’s earnings call. “No one was hurt. And the only evidence of the accident are a few scrapes and some minor damages on our truck.”

Hou noted that in the past seven years, TuSimple had accumulated 8.1 million miles of road testing with “precisely one incident.” When the incident happened on April 6, TuSimple grounded the entire fleet and began an independent investigation, said Hou. After determining the cause of the error, the company then upgraded all of its systems with an overhaul of its human machine interface to make sure the same problem would never happen again, the executive continued.

That internal report, which was reviewed by WSJ, revealed that the truck abruptly swerved left due to an outdated command, which was 2.5 minutes old and should have been erased from the system but wasn’t.

Researchers at Carnegie Mellon University told WSJ that common safeguards, had they been in place, would have prevented the crash. For example, the truck shouldn’t be responding to a command that’s even a couple hundredths of a second old, let alone more than two minutes old. The system also shouldn't be able to turn so sharply while traveling at 65 miles per hour, nor should a safety driver be able to engage a self-driving system that’s not properly functioning.