diff --git a/customize/customize_run.ml b/customize/customize_run.ml
index af1bf86f8..060eca3b3 100644
--- a/customize/customize_run.ml
+++ b/customize/customize_run.ml
@@ -198,20 +198,20 @@ exec >>%s 2>&1
     | `FirstbootCommand cmd ->
       incr i;
       msg (f_"Installing firstboot command: [%d] %s") !i cmd;
-      Firstboot.add_firstboot_script g root !i cmd
+      Firstboot.add_firstboot_script ~prog g root !i cmd
 
     | `FirstbootPackages pkgs ->
       incr i;
       msg (f_"Installing firstboot packages: [%d] %s") !i
         (String.concat " " pkgs);
       let cmd = guest_install_command pkgs in
-      Firstboot.add_firstboot_script g root !i cmd
+      Firstboot.add_firstboot_script ~prog g root !i cmd
 
     | `FirstbootScript script ->
       incr i;
       msg (f_"Installing firstboot script: [%d] %s") !i script;
       let cmd = read_whole_file script in
-      Firstboot.add_firstboot_script g root !i cmd
+      Firstboot.add_firstboot_script ~prog g root !i cmd
 
     | `Hostname hostname ->
       msg (f_"Setting the hostname: %s") hostname;
diff --git a/customize/firstboot.ml b/customize/firstboot.ml
index 211663712..3b9929b60 100644
--- a/customize/firstboot.ml
+++ b/customize/firstboot.ml
@@ -78,10 +78,7 @@ StandardError=inherit
 WantedBy=default.target
 " firstboot_dir
 
-let failed fs =
-  ksprintf (fun msg -> failwith (s_"firstboot: failed: " ^ msg)) fs
-
-let rec install_service (g : Guestfs.guestfs) distro =
+let rec install_service ~prog (g : Guestfs.guestfs) distro =
   g#mkdir_p firstboot_dir;
   g#mkdir_p (sprintf "%s/scripts" firstboot_dir);
   g#write (sprintf "%s/firstboot.sh" firstboot_dir) firstboot_sh;
@@ -97,7 +94,7 @@ let rec install_service (g : Guestfs.guestfs) distro =
   if g#is_dir "/etc/systemd/system" then
     install_systemd_service g;
   if g#is_dir "/etc/rc.d" || g#is_dir "/etc/init.d" then
-    install_sysvinit_service g distro
+    install_sysvinit_service ~prog g distro
 
 (* Install the systemd firstboot service, if not installed already. *)
 and install_systemd_service g =
@@ -106,7 +103,7 @@ and install_systemd_service g =
   g#ln_sf (sprintf "%s/firstboot.service" firstboot_dir)
     "/etc/systemd/system/default.target.wants"
 
-and install_sysvinit_service g = function
+and install_sysvinit_service ~prog g = function
   | "fedora"|"rhel"|"centos"|"scientificlinux"|"redhat-based" ->
     install_sysvinit_redhat g
   | "opensuse"|"sles"|"suse-based" ->
@@ -114,7 +111,7 @@ and install_sysvinit_service g = function
   | "debian"|"ubuntu" ->
     install_sysvinit_debian g
   | distro ->
-    failed "guest type %s is not supported" distro
+    error ~prog (f_"guest type %s is not supported") distro
 
 and install_sysvinit_redhat g =
   g#mkdir_p "/etc/rc.d/rc2.d";
@@ -155,12 +152,12 @@ and install_sysvinit_debian g =
   g#ln_sf "/etc/init.d/virt-sysprep-firstboot"
     "/etc/rc5.d/S99virt-sysprep-firstboot"
 
-let add_firstboot_script (g : Guestfs.guestfs) root i content =
+let add_firstboot_script ~prog (g : Guestfs.guestfs) root i content =
   let typ = g#inspect_get_type root in
   let distro = g#inspect_get_distro root in
   match typ, distro with
   | "linux", _ ->
-    install_service g distro;
+    install_service ~prog g distro;
     let t = Int64.of_float (Unix.time ()) in
     let r = string_random8 () in
     let filename = sprintf "%s/scripts/%04d-%Ld-%s" firstboot_dir i t r in
@@ -168,4 +165,4 @@ let add_firstboot_script (g : Guestfs.guestfs) root i content =
     g#chmod 0o755 filename
 
   | _ ->
-    failed "guest type %s/%s is not supported" typ distro
+    error ~prog (f_"guest type %s/%s is not supported") typ distro
diff --git a/customize/firstboot.mli b/customize/firstboot.mli
index b8d9608af..2aa8effe3 100644
--- a/customize/firstboot.mli
+++ b/customize/firstboot.mli
@@ -16,12 +16,13 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  *)
 
-val add_firstboot_script : Guestfs.guestfs -> string -> int -> string -> unit
-  (** [add_firstboot_script g root idx content] adds a firstboot
+val add_firstboot_script : prog:string -> Guestfs.guestfs -> string -> int -> string -> unit
+  (** [add_firstboot_script ~prog g root idx content] adds a firstboot
       script called [shortname] containing [content].
 
       NB. [content] is the contents of the script, {b not} a filename.
 
       The scripts run in index ([idx]) order.
 
-      You should make sure the filesystem is relabelled after calling this. *)
+      For Linux guests using SELinux you should make sure the
+      filesystem is relabelled after calling this. *)