diff --git a/builder/builder.ml b/builder/builder.ml
index b397fe232..3d0dbe7a8 100644
--- a/builder/builder.ml
+++ b/builder/builder.ml
@@ -110,7 +110,7 @@ let main () =
     printf "command line:";
     List.iter (printf " %s") (Array.to_list Sys.argv);
     print_newline ();
-    iteri (
+    List.iteri (
       fun i (source, fingerprint) ->
         printf "source[%d] = (%S, %S)\n" i source fingerprint
     ) cmdline.sources
@@ -576,7 +576,7 @@ let main () =
       | `Convert -> printf "qemu-img convert"
     in
 
-    iteri (
+    List.iteri (
       fun i (itags, task, otags) ->
         printf "%d: itags:" i;
         print_tags itags;
diff --git a/common/mlstdutils/std_utils.ml b/common/mlstdutils/std_utils.ml
index 37eef0348..fca76c208 100644
--- a/common/mlstdutils/std_utils.ml
+++ b/common/mlstdutils/std_utils.ml
@@ -81,14 +81,6 @@ end
 module String = struct
     include String
 
-    let map f s =
-      let len = String.length s in
-      let b = Bytes.create len in
-      for i = 0 to len-1 do
-        Bytes.unsafe_set b i (f (unsafe_get s i))
-      done;
-      Bytes.to_string b
-
     let lowercase_ascii s = map Char.lowercase_ascii s
     let uppercase_ascii s = map Char.uppercase_ascii s
 
@@ -493,8 +485,6 @@ and _wrap_find_next_break i len str =
 
 and output_spaces chan n = for i = 0 to n-1 do output_char chan ' ' done
 
-let (|>) x f = f x
-
 (* Drop elements from a list while a predicate is true. *)
 let rec dropwhile f = function
   | [] -> []
@@ -520,21 +510,6 @@ let rec find_map f = function
       | Some y -> y
       | None -> find_map f xs
 
-let iteri f xs =
-  let rec loop i = function
-    | [] -> ()
-    | x :: xs -> f i x; loop (i+1) xs
-  in
-  loop 0 xs
-
-let rec mapi i f =
-  function
-  | [] -> []
-  | a::l ->
-    let r = f i a in
-    r :: mapi (i + 1) f l
-let mapi f l = mapi 0 f l
-
 let rec combine3 xs ys zs =
   match xs, ys, zs with
   | [], [], [] -> []
diff --git a/common/mlstdutils/std_utils.mli b/common/mlstdutils/std_utils.mli
index c08e51360..786f42591 100644
--- a/common/mlstdutils/std_utils.mli
+++ b/common/mlstdutils/std_utils.mli
@@ -62,6 +62,8 @@ module String : sig
     val index : string -> char -> int
     val index_from : string -> int -> char -> int
     val iter : (char -> unit) -> string -> unit
+    val iteri : (int -> char -> unit) -> string -> unit
+    val map : (char -> char) -> string -> string
     val length : string -> int
     val make : int -> char -> string
     val rcontains_from : string -> int -> char -> bool
@@ -70,8 +72,6 @@ module String : sig
     val sub : string -> int -> int -> string
     val unsafe_get : string -> int -> char
 
-    val map : (char -> char) -> string -> string
-
     val lowercase_ascii : string -> string
     val uppercase_ascii : string -> string
     val capitalize_ascii : string -> string
@@ -195,10 +195,6 @@ val wrap : ?chan:out_channel -> ?indent:int -> string -> unit
 val output_spaces : out_channel -> int -> unit
 (** Write [n] spaces to [out_channel]. *)
 
-val (|>) : 'a -> ('a -> 'b) -> 'b
-(** Added in OCaml 4.01, we can remove our definition when we
-    can assume this minimum version of OCaml. *)
-
 val dropwhile : ('a -> bool) -> 'a list -> 'a list
 (** [dropwhile f xs] drops leading elements from [xs] until
     [f] returns false. *)
@@ -215,11 +211,6 @@ val find_map : ('a -> 'b option) -> 'a list -> 'b
 (** [find_map f xs] applies [f] to each element of [xs] until
     [f x] returns [Some y].  It returns [y].  If we exhaust the
     list then this raises [Not_found]. *)
-val iteri : (int -> 'a -> 'b) -> 'a list -> unit
-(** [iteri f xs] calls [f i x] for each element, with [i] counting from [0]. *)
-val mapi : (int -> 'a -> 'b) -> 'a list -> 'b list
-(** [mapi f xs] calls [f i x] for each element, with [i] counting from [0],
-    forming the return values from [f] into another list. *)
 
 val combine3 : 'a list -> 'b list -> 'c list -> ('a * 'b * 'c) list
 (** Like {!List.combine} but for triples.  All lists must be the same length. *)
diff --git a/common/mltools/tools_utils.ml b/common/mltools/tools_utils.ml
index 3355365c6..9049ab3f1 100644
--- a/common/mltools/tools_utils.ml
+++ b/common/mltools/tools_utils.ml
@@ -276,7 +276,7 @@ let external_command ?(echo_cmd = true) cmd =
 let rec run_commands ?(echo_cmd = true) cmds =
   let res = Array.make (List.length cmds) 0 in
   let pids =
-    mapi (
+    List.mapi (
       fun i (args, stdout_chan, stderr_chan) ->
         let run_res = do_run args ?stdout_chan ?stderr_chan in
         match run_res with
diff --git a/dib/dib.ml b/dib/dib.ml
index 5cbb10b09..9429d2371 100644
--- a/dib/dib.ml
+++ b/dib/dib.ml
@@ -990,7 +990,7 @@ let main () =
               [ csum_tool; fn ], Some outfd, None
           ) checksums in
         let res = run_commands cmds in
-        iteri (
+        List.iteri (
           fun i code ->
             if code <> 0 then (
               let args, _, _ = List.nth cmds i in
diff --git a/generator/OCaml.ml b/generator/OCaml.ml
index 9f880b55d..4f68eb7d5 100644
--- a/generator/OCaml.ml
+++ b/generator/OCaml.ml
@@ -497,7 +497,7 @@ copy_table (char * const * argv)
         pr "  CAMLlocal2 (rv, v);\n";
       pr "\n";
       pr "  rv = caml_alloc (%d, 0);\n" (List.length cols);
-      iteri (
+      List.iteri (
         fun i col ->
           (match col with
            | name, FString ->
@@ -774,7 +774,7 @@ copy_table (char * const * argv)
           name;
         pr "{\n";
         pr "  return guestfs_int_ocaml_%s (argv[0]" name;
-        iteri (fun i _ -> pr ", argv[%d]" (i+1)) (List.tl params);
+        List.iteri (fun i _ -> pr ", argv[%d]" (i+1)) (List.tl params);
         pr ");\n";
         pr "}\n";
         pr "\n"
diff --git a/generator/c.ml b/generator/c.ml
index 02d33ffc3..3eecb9ad2 100644
--- a/generator/c.ml
+++ b/generator/c.ml
@@ -648,7 +648,7 @@ extern GUESTFS_DLL_PUBLIC void *guestfs_next_private (guestfs_h *g, const char *
     pr "#define GUESTFS_HAVE_%s 1\n" (String.uppercase_ascii shortname);
 
     if optargs <> [] then (
-      iteri (
+      List.iteri (
         fun i argt ->
           let uc_shortname = String.uppercase_ascii shortname in
           let n = name_of_optargt argt in
@@ -677,7 +677,7 @@ extern GUESTFS_DLL_PUBLIC void *guestfs_next_private (guestfs_h *g, const char *
       pr "\n";
       pr "struct guestfs_%s_argv {\n" shortname;
       pr "  uint64_t bitmask;\n";
-      iteri (
+      List.iteri (
         fun i argt ->
           let c_type =
             match argt with
diff --git a/generator/daemon.ml b/generator/daemon.ml
index b8ee4081f..3298e04ec 100644
--- a/generator/daemon.ml
+++ b/generator/daemon.ml
@@ -48,7 +48,7 @@ let generate_daemon_actions_h () =
     function
     | { style = _, _, [] } -> ()
     | { name = shortname; style = _, _, (_::_ as optargs) } ->
-        iteri (
+        List.iteri (
           fun i arg ->
             let uc_shortname = String.uppercase_ascii shortname in
             let n = name_of_optargt arg in
@@ -535,7 +535,7 @@ let generate_daemon_caml_stubs () =
     pr "    return NULL;\n";
     pr "  }\n";
     pr "\n";
-    iteri (
+    List.iteri (
       fun i ->
         pr "  v = Field (retv, %d);\n" i;
         function
diff --git a/generator/erlang.ml b/generator/erlang.ml
index 5d5253278..8e70cfbd4 100644
--- a/generator/erlang.ml
+++ b/generator/erlang.ml
@@ -288,7 +288,7 @@ instead of erl_interface.
       pr "{\n";
       pr "  ETERM *t[%d];\n" (List.length cols);
       pr "\n";
-      iteri (
+      List.iteri (
         fun i col ->
           (match col with
            | name, FString ->
@@ -358,7 +358,7 @@ instead of erl_interface.
       pr "run_%s (ETERM *args_tuple)\n" name;
       pr "{\n";
 
-      iteri (
+      List.iteri (
         fun i ->
           function
           | String (_, n) ->
diff --git a/generator/events.ml b/generator/events.ml
index f3b682a5a..6c45a3723 100644
--- a/generator/events.ml
+++ b/generator/events.ml
@@ -44,6 +44,6 @@ let events = [
   "warning";                            (* warnings from the library *)
 ]
 
-let events = mapi (fun i name -> name, 1 lsl i) events
+let events = List.mapi (fun i name -> name, 1 lsl i) events
 
 let all_events_bitmask = (1 lsl List.length events) - 1
diff --git a/generator/fish.ml b/generator/fish.ml
index e34022ac5..aeb57dd4c 100644
--- a/generator/fish.ml
+++ b/generator/fish.ml
@@ -1165,7 +1165,7 @@ $VG guestfish \\
 
   let vg_count = ref 0 in
 
-  iteri (
+  List.iteri (
     fun i (name, _, _, _) ->
       let params = [name] in
       let params =
diff --git a/generator/java.ml b/generator/java.ml
index 308f65bd8..157c2bf5b 100644
--- a/generator/java.ml
+++ b/generator/java.ml
@@ -330,7 +330,7 @@ public class GuestFS {
         pr "    /* Unpack optional args. */\n";
         pr "    Object _optobj;\n";
         pr "    long _optargs_bitmask = 0;\n";
-        iteri (
+        List.iteri (
           fun i argt ->
             let t, boxed_t, convert, n, default =
               match argt with
diff --git a/generator/lua.ml b/generator/lua.ml
index f544ce07a..dd6aedbe9 100644
--- a/generator/lua.ml
+++ b/generator/lua.ml
@@ -493,7 +493,7 @@ guestfs_int_lua_delete_event_callback (lua_State *L)
       pr "                       \"%s\");\n" name;
       pr "\n";
 
-      iteri (
+      List.iteri (
         fun i ->
           let i = i+2 in (* Lua indexes from 1(!), plus the handle. *)
           function
diff --git a/generator/perl.ml b/generator/perl.ml
index 31a1d194f..6fe308213 100644
--- a/generator/perl.ml
+++ b/generator/perl.ml
@@ -353,7 +353,7 @@ PREINIT:
         pr ", ...";
       pr ")\n";
       pr "      guestfs_h *g;\n";
-      iteri (
+      List.iteri (
         fun i ->
           function
           | String (_, n) ->
diff --git a/generator/python.ml b/generator/python.ml
index 796e26aa5..5d4a1e9d0 100644
--- a/generator/python.ml
+++ b/generator/python.ml
@@ -873,7 +873,7 @@ class GuestFS(object):
              * at the end.
              *)
             let lines =
-              mapi (
+              List.mapi (
                 fun lineno line ->
                   if line = "" && lineno <> endpos then
                     ""
diff --git a/generator/ruby.ml b/generator/ruby.ml
index 308dd589b..3bd81b723 100644
--- a/generator/ruby.ml
+++ b/generator/ruby.ml
@@ -240,7 +240,7 @@ and generate_ruby_c actions () =
         pr "  if (argc < %d || argc > %d)\n" nr_args (nr_args+1);
         pr "    rb_raise (rb_eArgError, \"expecting %d or %d arguments\");\n" nr_args (nr_args+1);
         pr "\n";
-        iteri (
+        List.iteri (
           fun i arg ->
             pr "  volatile VALUE %sv = argv[%d];\n" (name_of_argt arg) i
         ) args;
diff --git a/generator/tests_c_api.ml b/generator/tests_c_api.ml
index eafae3368..33da61181 100644
--- a/generator/tests_c_api.ml
+++ b/generator/tests_c_api.ml
@@ -99,7 +99,7 @@ let rec generate_c_api_tests () =
   let test_names =
     List.map (
       fun { name; optional; tests } ->
-        mapi (generate_one_test name optional) tests
+        List.mapi (generate_one_test name optional) tests
     ) (actions |> sort) in
   let test_names = List.concat test_names in
 
@@ -274,7 +274,7 @@ and generate_test_perform name i test_name test =
   | TestResult (seq, expr) ->
     pr "  /* TestResult for %s (%d) */\n" name i;
     let n = List.length seq in
-    iteri (
+    List.iteri (
       fun i cmd ->
         let ret = if i = n-1 then "ret" else sprintf "ret%d" (n-i-1) in
         generate_test_command_call ~ret test_name cmd
@@ -430,12 +430,12 @@ and generate_test_command_call ?(expect_error = false) ?(do_return = true) ?test
       pr "  const char *const %s[1] = { NULL };\n" sym
     | StringList (_, _), arg, sym ->
       let strs = String.nsplit " " arg in
-      iteri (
+      List.iteri (
         fun i str ->
           pr "  const char *%s_%d = \"%s\";\n" sym i (c_quote str);
       ) strs;
       pr "  const char *const %s[] = {\n" sym;
-      iteri (
+      List.iteri (
         fun i _ -> pr "    %s_%d,\n" sym i
       ) strs;
       pr "    NULL\n";
@@ -478,12 +478,12 @@ and generate_test_command_call ?(expect_error = false) ?(do_return = true) ?test
             pr "  const char *const %s[1] = { NULL };\n" n; true
           | OStringList n, arg ->
             let strs = String.nsplit " " arg in
-            iteri (
+            List.iteri (
               fun i str ->
                 pr "  const char *%s_%d = \"%s\";\n" n i (c_quote str);
             ) strs;
             pr "  const char *const %s[] = {\n" n;
-            iteri (
+            List.iteri (
               fun i _ -> pr "    %s_%d,\n" n i
             ) strs;
             pr "    NULL\n";
diff --git a/v2v/convert_linux.ml b/v2v/convert_linux.ml
index 6c1d9afff..81e195866 100644
--- a/v2v/convert_linux.ml
+++ b/v2v/convert_linux.ml
@@ -921,7 +921,7 @@ let convert (g : G.guestfs) inspect source output rcaps =
       | IDE -> ide_block_prefix in
 
     let map =
-      mapi (
+      List.mapi (
         fun i disk ->
           let block_prefix_before_conversion =
             match disk.s_controller with
@@ -945,7 +945,7 @@ let convert (g : G.guestfs) inspect source output rcaps =
      * although the guest uses xvdX natively.
      *)
     let map = map @
-      mapi (
+      List.mapi (
         fun i disk ->
           "xvd" ^ drive_name i, block_prefix_after_conversion ^ drive_name i
       ) source.s_disks in
diff --git a/v2v/copy_to_local.ml b/v2v/copy_to_local.ml
index 108eb35ab..d92ad0f88 100644
--- a/v2v/copy_to_local.ml
+++ b/v2v/copy_to_local.ml
@@ -174,7 +174,7 @@ read the man page virt-v2v-copy-to-local(1).
 
   (* Copy the disks. *)
   let n = List.length disks in
-  iteri (
+  List.iteri (
     fun i (remote_disk, local_disk, sslverify, cookie) ->
     message (f_"Copying remote disk %d/%d to %s")
             (i+1) n local_disk;
diff --git a/v2v/create_ovf.ml b/v2v/create_ovf.ml
index 01f966769..1b851b0e9 100644
--- a/v2v/create_ovf.ml
+++ b/v2v/create_ovf.ml
@@ -478,7 +478,7 @@ and add_disks targets guestcaps output_alloc sd_uuid image_uuids vol_uuids ovf =
     with Not_found -> assert false in
 
   (* Iterate over the disks, adding them to the OVF document. *)
-  iteri (
+  List.iteri (
     fun i ({ target_overlay = ov } as t, image_uuid, vol_uuid) ->
       (* This sets the boot order to boot the first disk first.  This
        * isn't generally correct.  We should copy over the boot order
@@ -604,7 +604,7 @@ and add_networks nics guestcaps ovf =
     with Not_found -> assert false in
 
   (* Iterate over the NICs, adding them to the OVF document. *)
-  iteri (
+  List.iteri (
     fun i { s_mac = mac; s_vnet_type = vnet_type;
             s_vnet = vnet; s_vnet_orig = vnet_orig } ->
       let dev = sprintf "eth%d" i in
diff --git a/v2v/input_vmx.ml b/v2v/input_vmx.ml
index 012e23aaf..366e63560 100644
--- a/v2v/input_vmx.ml
+++ b/v2v/input_vmx.ml
@@ -118,7 +118,7 @@ and find_hdds vmx vmx_filename
   let hdds = List.map (fun (_, _, source) -> source) hdds in
 
   (* Set the s_disk_id field to an incrementing number. *)
-  let hdds = mapi (fun i source -> { source with s_disk_id = i }) hdds in
+  let hdds = List.mapi (fun i source -> { source with s_disk_id = i }) hdds in
 
   hdds
 
diff --git a/v2v/inspect_source.ml b/v2v/inspect_source.ml
index 00197e2fa..05d3a6ca3 100644
--- a/v2v/inspect_source.ml
+++ b/v2v/inspect_source.ml
@@ -121,7 +121,7 @@ and choose_root root_choice g = function
         printf "\n***\n";
         printf (f_"Dual- or multi-boot operating system detected.  Choose the root filesystem\nthat contains the main operating system from the list below:\n");
         printf "\n";
-        iteri (
+        List.iteri (
           fun i root ->
             let prod = g#inspect_get_product_name root in
             match prod with
diff --git a/v2v/output_glance.ml b/v2v/output_glance.ml
index 2f57a67d1..4e4f965c1 100644
--- a/v2v/output_glance.ml
+++ b/v2v/output_glance.ml
@@ -144,7 +144,7 @@ object
      * will be called "guestname-disk2" etc.  The manual strongly
      * hints you should import the data disks to Cinder.
      *)
-    iteri (
+    List.iteri (
       fun i { target_file; target_format } ->
         let name =
           if i == 0 then source.s_name
diff --git a/v2v/output_qemu.ml b/v2v/output_qemu.ml
index 6e59f1932..d18b4b7c9 100644
--- a/v2v/output_qemu.ml
+++ b/v2v/output_qemu.ml
@@ -164,7 +164,7 @@ object
       | Virtio_net -> "virtio-net-pci"
       | E1000 -> "e1000"
       | RTL8139 -> "rtl8139" in
-    iteri (
+    List.iteri (
       fun i nic ->
         arg_list "-netdev" ["user"; "id=net" ^ string_of_int i];
         arg_list "-device" [net_bus;
diff --git a/v2v/target_bus_assignment.ml b/v2v/target_bus_assignment.ml
index b15a519e7..83b77914f 100644
--- a/v2v/target_bus_assignment.ml
+++ b/v2v/target_bus_assignment.ml
@@ -37,7 +37,7 @@ let rec target_bus_assignment source targets guestcaps =
       | Virtio_blk -> virtio_blk_bus
       | Virtio_SCSI -> scsi_bus
       | IDE -> ide_bus in
-    iteri (
+    List.iteri (
       fun i t ->
         let t = BusSlotTarget t in
         insert bus i t
diff --git a/v2v/v2v.ml b/v2v/v2v.ml
index 4a1a50317..75a8c254e 100644
--- a/v2v/v2v.ml
+++ b/v2v/v2v.ml
@@ -282,7 +282,7 @@ and check_host_free_space () =
 (* Create a qcow2 v3 overlay to protect the source image(s). *)
 and create_overlays src_disks =
   message (f_"Creating an overlay to protect the source from being modified");
-  mapi (
+  List.mapi (
     fun i ({ s_qemu_uri = qemu_uri; s_format = format } as source) ->
       let overlay_file =
         Filename.temp_file ~temp_dir:overlay_dir "v2vovl" ".qcow2" in
@@ -664,7 +664,7 @@ and copy_targets cmdline targets input output =
     )
   );
   let nr_disks = List.length targets in
-  mapi (
+  List.mapi (
     fun i t ->
       message (f_"Copying disk %d/%d to %s (%s)")
         (i+1) nr_disks t.target_file t.target_format;