Tesla has been ordered to recall nearly 4,000 of its Cybertrucks due to an accelerator pedal that can stick in place when pressed down.

The cause, according to the regulator: soap.

“An unapproved change introduced lubricant (soap) to aid in the component assembly of the pad onto the accelerator pedal. Residual lubricant reduced the retention of the pad to the pedal,” the NHTSA wrote in the recall document.

Tesla has yet to detail how many of the futuristic looking Cybertrucks it has produced. But it has said that it would be slow ramping up production of the vehicle, which had its first deliveries in late November.

The NHTSA said the recall affects “all Model Year (‘MY’) 2024 Cybertruck vehicles manufactured from November 13, 2023, to April 4, 2024.”

That means the 3,878 trucks being recalled are likely many, if not all, of the trucks now on US roads.

Documents from the National Highway Traffic Safety Administration about the recall say that “when high force is applied to the pad on the accelerator pedal, the pad may dislodge, which may cause the pedal to become trapped in the interior trim above the pedal.”

The safety regulator said workers assembling the trucks at Tesla’s factory near Austin, Texas, improperly used soap to aid in the component assembly of the pad onto the accelerator pedal.

The accelerator sticking issue was first raised in social media and online discussion group posts.

On Monday, NHTSA told CNN it had reached out to Tesla requesting more information on the issue.

Telsa did not immediately respond to a request for comment. The company this month told employees it would lay off roughly 10% of its global workforce.

Unlike many Tesla recalls, this one cannot be fixed with a simple over-the-air software update. Tesla will have to have owners respond to letters and bring the Cybertrucks into its service centers for a repair at no charge.