Zoox has issued a software recall after one of its robotaxis struggled to navigate a smoke-filled emergency fire scene in June.

The Amazon-owned company said Friday that it has shipped to its fleet of 105 vehicles a software update that should address the issue. Zoox told TechCrunch in a statement that the software update “enhances the existing capability of detecting active [emergency] scenes by adding the ability to detect and respond to heavy smoke in certain situations.”

Nobody was on board the vehicle during the June incident, and Zoox told the National Highway Traffic Safety Administration (NHTSA) that it is not aware of injuries associated with the problem. The NHTSA’s report doesn’t state where the June incident took place, and Zoox declined to say.

Zoox’s recall comes just a week after NHTSA administrator Jonathan Morrison sent a letter to self-driving car companies warning them to stop interfering with first responders.

“Let me be clear: the inability to detect and appropriately respond to such situations represents a functional insufficiency,” he wrote. “Emergency scenes are not rare or extreme ‘edge cases.’ As such, NHTSA is today issuing a call to action for AV developers and operators to immediately focus their resources on fixing this issue.”