alma chroot fails

[phillipwood]

When I run

sudo alma chroot /dev/sdc

on an install created with sudo alma -i -e /dev/sdc I get

Enter passphrase for /dev/sdc3: 
 2021-07-09T10:01:20.527Z INFO  alma::tool::mount > Mounting filesystems to /tmp/.tmpeBuuXs
mount: /tmp/.tmpeBuuXs/proc: mount point does not exist.
==> ERROR: failed to setup chroot /tmp/.tmpeBuuXs
Error: Error running command in chroot: 

Caused by:
    Bad exit code: exit status: 1

When I ran the installation the chroot for the -i flag worked fine, it's only after removing the usb stick and putting it back in that it has stopped working. I'm using 'alma-git' from the aur, the version is r118.6b49b5f-1, it also fails with alma from the aur (which is what I used for the install).