diff --git a/tools/gen_signatures_registry.ml b/tools/gen_signatures_registry.ml
index 15dd0ad8..39804093 100644
--- a/tools/gen_signatures_registry.ml
+++ b/tools/gen_signatures_registry.ml
@@ -57,38 +57,40 @@ type purpose = {
   comment: string;
 }
 
-let f records =
-  records
-  |> List.filter_map (fun l ->
-      match l with
-      | a :: b :: c :: _ -> (
-          match a.k = "Number" && b.k = "Name" && c.k = "Comment" with
-          | false -> None
-          | true ->
-              Some
-                {
-                  number= Int32.of_int (int_of_string a.v);
-                  name= b.v;
-                  comment= c.v;
-                })
-      | _ -> None)
-  |>
-  (*GNU Taler, >= 1000*)
-  List.filter (fun v -> v.number >= 1000_l)
-
 let read_file file = In_channel.with_open_bin file In_channel.input_all
-let file_header = {|...|}
 
 let () =
   let content = read_file "registry.rec" in
   match parse content with
   | Error msg -> Fmt.failwith "Parse error: %s" msg
   | Ok records ->
-      let purposes = f records in
+      let purposes =
+        records
+        |> List.filter_map (fun l ->
+            match l with
+            | a :: b :: c :: _ -> (
+                match a.k = "Number" && b.k = "Name" && c.k = "Comment" with
+                | false -> None
+                | true ->
+                    Some
+                      {
+                        number= Int32.of_int (int_of_string a.v);
+                        name= b.v;
+                        comment= c.v;
+                      })
+            | _ -> None)
+        |> List.filter (fun v -> v.number >= 1000_l)
+      in
+
+      let header =
+        {|(* This file was generated from the GANA database:
+        https://git-www.gnunet.org/gana.git/tree/gnunet-signatures/registry.rec *)
+        |}
+      in
 
       let pp_purpose ppf { number; name; comment } =
         Fmt.pf ppf "(** %s *)\nlet %s : int32 = %ld\n\n" comment name number
       in
 
-      Fmt.pr "%a@." (Fmt.list ~sep:Fmt.nop pp_purpose) purposes;
+      Fmt.pr "%s\n\n%a@." header (Fmt.list ~sep:Fmt.nop pp_purpose) purposes;
       ()