Most recalls through the U.S. National Highway Traffic Safety Administration are for problems that aren’t great but sound rather normal, like , , or . But a new, nearly 560,000-truck General Motors recall sounds like something out of a Mad Lib: Seat belts in the affected vehicles could, in the right conditions, end up causing a fire.

Yes, seat belts. How, you ask? Great question.

Certain Silverado 1500 and Sierra 1500 models from the 2019 and 2020 model year are on the list in the , as well as 2020 Silverado and Sierra 2500s and 3500s. Of the 556,399 included in the recall, the estimated amount of trucks with the defect is 1 percent.

The potential problem with the trucks, essentially, is that in a crash that would cause the seat-belt pretensioners—the mechanisms that —to engage, a fire could start near the B-pillar. That’s only the case for trucks with carpet, and the recall documents explain the issue well:

There is a small opening in the pretensioner bracket that can allow gasses expelled from a pretensioner during deployment to come into contact with cotton material in the carpet floor. This opening was intended as a locator hole for assembly but was never utilized. It was not a part of the pretensioner system performance design.

[...] Following a crash that causes the seatbelt pretensioners to deploy, smoke or a burning odor from the area at the base of the B-pillar may be noticeable before a fire propagates sufficiently to be visible.

The documents say GM was notified about a fire in July, and that it opened a product investigation in September. There were no reports of crashes or injuries related to the issue, according to the documents, GM decided to conduct a recall on Nov. 7.

To fix the issue, recall documents say dealers will close off the opening in the pretensioner bracket so that the exhaust gasses from the system get sent away from the carpet, thus keeping it from igniting. Dealers heard about the recall on Nov. 14, and one document says GM “will provide owner letter notification dates when available” while says it’ll begin early in December.