diff --git a/builder/cmdline.ml b/builder/cmdline.ml
index 49a57eeba..73ffd122b 100644
--- a/builder/cmdline.ml
+++ b/builder/cmdline.ml
@@ -43,7 +43,7 @@ type cmdline = {
   delete_on_failure : bool;
   format : string option;
   gpg : string;
-  list_format : [`Short|`Long|`Json];
+  list_format : List_entries.format;
   memsize : int option;
   network : bool;
   ops : Customize_cmdline.ops;
@@ -89,15 +89,13 @@ let parse_cmdline () =
   let format = ref "" in
   let gpg = ref "gpg" in
 
-  let list_format = ref `Short in
-  let list_set_long () = list_format := `Long in
+  let list_format = ref List_entries.Short in
+  let list_set_long () = list_format := List_entries.Long in
   let list_set_format arg =
-    list_format := match arg with
-    | "short" -> `Short
-    | "long" -> `Long
-    | "json" -> `Json
-    | fmt ->
-      error (f_"invalid --list-format type '%s', see the man page") fmt in
+    (* Do not catch the Invalid_argument that list_format_of_string
+     * throws on invalid input, as it is already checked by the
+     * Getopt handling of Symbol. *)
+    list_format := List_entries.list_format_of_string arg in
 
   let machine_readable = ref false in
 
@@ -119,6 +117,9 @@ let parse_cmdline () =
   let sync = ref true in
   let warn_if_partition = ref true in
 
+  let formats = List_entries.list_formats
+  and formats_string = String.concat "|" List_entries.list_formats in
+
   let argspec = [
     [ L"arch" ],    Getopt.Set_string ("arch", arch),        s_"Set the output architecture";
     [ L"attach" ],  Getopt.String ("iso", attach_disk),     s_"Attach data disk/ISO during install";
@@ -145,7 +146,7 @@ let parse_cmdline () =
     [ L"gpg" ],    Getopt.Set_string ("gpg", gpg),          s_"Set GPG binary/command";
     [ S 'l'; L"list" ],        Getopt.Unit list_mode,        s_"List available templates";
     [ L"long" ],    Getopt.Unit list_set_long,    s_"Shortcut for --list-format long";
-    [ L"list-format" ], Getopt.String ("short|long|json", list_set_format),
+    [ L"list-format" ], Getopt.Symbol (formats_string, formats, list_set_format),
                                              s_"Set the format for --list (default: short)";
     [ L"machine-readable" ], Getopt.Set machine_readable, s_"Make output machine readable";
     [ S 'm'; L"memsize" ],        Getopt.Int ("mb", set_memsize),        s_"Set memory size";
diff --git a/builder/cmdline.mli b/builder/cmdline.mli
index 854db618f..a0517a25d 100644
--- a/builder/cmdline.mli
+++ b/builder/cmdline.mli
@@ -30,7 +30,7 @@ type cmdline = {
   delete_on_failure : bool;
   format : string option;
   gpg : string;
-  list_format : [`Short|`Long|`Json];
+  list_format : List_entries.format;
   memsize : int option;
   network : bool;
   ops : Customize_cmdline.ops;
diff --git a/builder/list_entries.ml b/builder/list_entries.ml
index 2f053e8a9..2a1aef4c8 100644
--- a/builder/list_entries.ml
+++ b/builder/list_entries.ml
@@ -21,11 +21,24 @@ open Common_utils
 
 open Printf
 
+type format =
+  | Short
+  | Long
+  | Json
+
+let list_formats = [ "short"; "long"; "json" ]
+
+let list_format_of_string = function
+  | "short" -> Short
+  | "long" -> Long
+  | "json" -> Json
+  | fmt -> invalid_arg fmt
+
 let rec list_entries ~list_format ~sources index =
   match list_format with
-  | `Short -> list_entries_short index
-  | `Long -> list_entries_long ~sources index
-  | `Json -> list_entries_json ~sources index
+  | Short -> list_entries_short index
+  | Long -> list_entries_long ~sources index
+  | Json -> list_entries_json ~sources index
 
 and list_entries_short index =
   List.iter (
diff --git a/builder/list_entries.mli b/builder/list_entries.mli
index a3f35d39b..008b90623 100644
--- a/builder/list_entries.mli
+++ b/builder/list_entries.mli
@@ -16,4 +16,18 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  *)
 
-val list_entries : list_format:([ `Short | `Long | `Json ]) -> sources:Sources.source list -> Index.index -> unit
+type format =
+  | Short
+  | Long
+  | Json
+
+val list_formats : string list
+(** The string representation of the available formats. *)
+
+val list_format_of_string : string -> format
+(** Convert from a string to the corresponding format.
+
+    Throw [Invalid_argument] if the string does not match any
+    valid format. *)
+
+val list_entries : list_format:format -> sources:Sources.source list -> Index.index -> unit