It looks like:- https://bugzilla.redhat.com/show_bug.cgi?id=1078057 I am hitting it on a UEFI disk /dev/sda1, which is mounted as /boot/efi The RedHat bug says this is a regression introduced in dosfstools-3.0.26. It seems to work with dosfstools-3.0.25. I am running 3.0.26-4. David