diff --git a/build_library/qemu_template.sh b/build_library/qemu_template.sh
index 3621956a53..e8a0b019c1 100755
--- a/build_library/qemu_template.sh
+++ b/build_library/qemu_template.sh
@@ -21,6 +21,7 @@ SAFE_ARGS=0
 USAGE="Usage: $0 [-a authorized_keys] [--] [qemu options...]
 Options:
     -i FILE     File containing an Ignition config
+                (needs \"-append 'flatcar.first_boot=1'\" for already-booted or PXE images)
     -u FILE     Cloudinit user-data as either a cloud config or script.
     -c FILE     Config drive as an iso or fat filesystem image.
     -a FILE     SSH public keys for login access. [~/.ssh/id_{dsa,rsa}.pub]