[Libguestfs] err from guestfs_launch

[Skippy VonDrake]

This error is with libguestfs 1.20.
Calling guestfs_launch() with tracing on:

supermin helper [00065ms] finished creating appliance
libguestfs: checksum of existing appliance:
2bd6811426e14b6fb661b4d52cebd6c21a41df1a068e8acf6a7a08e3b3bd4ada
libguestfs: trace: get_cachedir
libguestfs: trace: get_cachedir = "/var/tmp"
libguestfs: [00071ms] begin building supermin appliance
libguestfs: trace: get_cachedir
libguestfs: trace: get_cachedir = "/var/tmp"
libguestfs: [00071ms] run febootstrap-supermin-helper
libguestfs: command: run: febootstrap-supermin-helper
libguestfs: command: run: \ --verbose
libguestfs: command: run: \ --copy-kernel
libguestfs: command: run: \ -f ext2
libguestfs: command: run: \ /usr/local/lib/guestfs/supermin.d
libguestfs: command: run: \ x86_64
libguestfs: command: run: \ /var/tmp/guestfs.lQs0RL/kernel
libguestfs: command: run: \ /var/tmp/guestfs.lQs0RL/initrd
libguestfs: command: run: \ /var/tmp/guestfs.lQs0RL/root
febootstrap-supermin-helper: unrecognized option '--copy-kernel'
febootstrap-supermin-helper: build the supermin appliance on the fly

Usage:
  febootstrap-supermin-helper [-options] inputs [...] host_cpu kernel initrd
<snip>

Same code works on a different system.  Both systems are Ubuntu 12.04.
However the system that works is using Linux 3.6.4-pv whereas the system
that fails is Linux 3.5.4-pv.

Do I need to upgrade the kernel?