The first public release of macOS Monterey contained a serious bug that affected some older Macs with the T2 chip. Now Apple has released updated bridgeOS firmware to solve the problem, reports 9to5Mac.

This should fix the problem for owners of T2-equipped Macs who update to the latest version of macOS Monterey. Any user who was affected by the bug before the update arrived is encouraged to contact Apple's customer service department.

"We have identified and fixed an issue with the firmware on the Apple T2 security chip that prevented a very small number of users from booting up their Mac after updating macOS," Apple has said in a statement. "The updated firmware is now included with the existing macOS updates. Any users impacted by this issue can contact Apple Support for assistance."

Shortly after Monterey's launch, there were concerning reports that some Macs were being bricked by the update. The problem seemed to be affecting older Intel-based models.

The following Mac models have a T2 chip, and may therefore be affected:

  • iMac 27in (Retina 5K, 2020)
  • iMac Pro
  • Mac Pro (2019)
  • Mac Pro (Rack model, 2019)
  • Mac mini (2018)
  • MacBook Air 13in (Retina, 2020)
  • MacBook Air 13in (Retina, 2019)
  • MacBook Air 13in (Retina, 2018)
  • MacBook Pro 13in (2020, 2 x Thunderbolt 3 ports)
  • MacBook Pro 13in (2020, 4 x Thunderbolt 3 ports)
  • MacBook Pro 16in (2019)
  • MacBook Pro 13in (2019, 2 x Thunderbolt 3 ports)
  • MacBook Pro 15in (2019)
  • MacBook Pro 13in (2019, 4 x Thunderbolt 3 ports)
  • MacBook Pro 15in (2018)
  • MacBook Pro 13in (2018, 4 x Thunderbolt 3 ports)

The T2 chip has caused headaches before now. Last year we reported on claims that it's a nightmare for repairers, and contained a serious vulnerability.

This article originally appeared on Macworld Sweden. Translation (using DeepL) and additional reporting by David Price.