Upgrading to High Sierra: “You may not install this volume because the computer is missing a firmware partition”

If you try to upgrade to High Sierra (macOS 10.13) and get You may not install this volume because the computer is missing a firmware partition when trying to select your drive to upgrade, it may be because you're upgrading on an OWC drive.

If you're using Munki, the error may appear in your /Library/Managed Installs/Logs/Install.log as Starting macOS install: FAILED: startosinstall failed with return code 243.

Previously, you'd have to physically swap back the OEM drive, and then put the OWC drive back again, but now OWC has its own firmware updater tool that fixes the problem:
Aura SSDs: Firmware Update (beta).


  1. The Aura SSD firmware updater is NOT for Mac Pro users. Supposedly it works on MacBook, MacBook Pro, Mac Mini, and God knows what else…but if you have a Black Trashcan, you’re SOL. As far as I’ve been able to tell, the only way to get the firmware update is to shut down, uninstall the Aura SSD, reinstall the original Apple factory SSD, run the High Sierra (or Mojave) installer, and (allegedly) that will enable the Mac to view the Aura SSD as a proper internal drive. Then you reinstall the Aura SSD and run the High Sierra (or Mojave) installer on the Aura SSD. At least, that’s the way the story goes. I haven’t tried it yet. I’m waiting until OWC Tech Support is available (it’s Sunday now; they’re gone), and I’m going to ask them if there are any other options.

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