Apple announced macOS High Sierra earlier this year with a slew of new features, including a brand new file system aptly called Apple File System, or APFS for short. The feature was set to arrive with the High Sierra update for all compatible Macs, but now it’ll only be available to computers with all-flash built-in storage.

In early versions of the macOS High Sierra beta, Fusion drive and hard drive Macs were converted to the new APFS, but later updates removed it. Now, with the Golden Master version of High Sierra available, Apple has confirmed that Fusion drive and hard drive machines won’t work with the new file system at all.

Early beta adopters who were stuck with High Sierra were given instructions by Apple on how to convert back from APFS to the standard HFS+. It is a long and arduous chore with lots of steps.

It’s a shame as APFS offers a ton of new features like stability, safe back ups, improved performance and stronger encryption. Older Macs won’t be able to take advantage of the new feature. Apple hasn’t mentioned if support for Fusion drives or hard drives will arrive in the future.

Apple’s macOS High Sierra update will roll out September 25.