If you try to turn on FileVault, and get an erroneous warning stating “A recovery key has been set by your company, school or institution”, delete these two files and reboot:

  • /Library/Keychains/FileVaultMaster.cer
  • /Library/Keychains/FileVaultMaster.keychain

This can be caused if you used Apple Migration Assistant in the past to move over data from an older Mac, and that Mac had FileVault turned on and back off again.