Electric car maker Tesla Motors Inc said it is recalling 1,228 of its 2013 Model S cars manufactured between May 10 and June 8 due to a defect in the mounting bracket of the rear seat.

“This reduces our confidence that the left hand seat back will be properly retained in the event of a crash,” Tesla founder and Chief Executive Elon Musk said in a statement on Wednesday posted on the company’s website.

The recall blemishes a clean public record for the Model S, which received a near-perfect score from the influential Consumer Reports magazine.

In a filing, the National Highway Traffic Safety Administration (NHTSA) said in the event of a crash, if the seat becomes unmoored, there is an increased chance of injury to a passenger.

Musk said there have been no customer complaints and that the company was not aware of any injuries because of the defect. The recall was not in response to any regulatory warning, he said.

Tesla said in its filing with the NHTSA that it suspected that 20 percent of the 1,228 vehicles have welds that may not hold in the event of a crash.

A worker at the plant’s assembly line in California noticed the defect and reported it to managers, Tesla told NHTSA.