diff --git a/daemon/devsparts.ml b/daemon/devsparts.ml
index c082c32fb..59e66e82e 100644
--- a/daemon/devsparts.ml
+++ b/daemon/devsparts.ml
@@ -111,14 +111,3 @@ let is_whole_device device =
 
   try ignore (stat devpath); true
   with Unix_error ((ENOENT|ENOTDIR), _, _) -> false
-
-let device_index device =
-  (* This is the algorithm which was used by the C version.  Why
-   * can't we use drive_index from C_utils?  XXX
-   *)
-  let rec loop i = function
-    | [] -> failwithf "%s: device not found" device
-    | dev :: devices when dev = device -> i
-    | _ :: devices -> loop (i+1) devices
-  in
-  loop 0 (list_devices ())
diff --git a/daemon/inspect_utils.ml b/daemon/inspect_utils.ml
index ea444afe6..e9aa8221f 100644
--- a/daemon/inspect_utils.ml
+++ b/daemon/inspect_utils.ml
@@ -148,11 +148,7 @@ and is_dir_nocase path =
  * the old C inspection code.  XXX fix function and callers
  *)
 let is_partition partition =
-  try
-    let device = Devsparts.part_to_dev partition in
-    ignore (Devsparts.device_index device);
-    true
-  with _ -> false
+  try Devsparts.part_to_dev partition <> partition with _ -> false
 
 let re_major_minor = PCRE.compile "(\\d+)\\.(\\d+)"
 let re_major_no_minor = PCRE.compile "(\\d+)"
diff --git a/generator/actions_core.ml b/generator/actions_core.ml
index 692015e27..eca52d347 100644
--- a/generator/actions_core.ml
+++ b/generator/actions_core.ml
@@ -739,6 +739,23 @@ Converted to F</dev/VG/LV> form using C<guestfs_lvm_canonical_lv_name>.
 
 Other strings are returned unmodified." };
 
+  { defaults with
+    name = "device_index"; added = (1, 19, 7);
+    style = RInt "index", [String (Device, "device")], [];
+    tests = [
+      InitEmpty, Always, TestResult (
+        [["device_index"; "/dev/sda"]], "ret == 0"), []
+    ];
+    shortdesc = "convert device to index";
+    longdesc = "\
+This function takes a device name (eg. \"/dev/sdb\") and
+returns the index of the device in the list of devices.
+
+Index numbers start from 0.  The named device must exist,
+for example as a string returned from C<guestfs_list_devices>.
+
+See also C<guestfs_list_devices>, C<guestfs_part_to_dev>." };
+
   { defaults with
     name = "shutdown"; added = (1, 19, 16);
     style = RErr, [], [];
@@ -7423,24 +7440,6 @@ different operation that turns free space in the filesystem
 into zeroes.  It is valid to call C<guestfs_fstrim> either
 instead of, or after calling C<guestfs_zero_free_space>." };
 
-  { defaults with
-    name = "device_index"; added = (1, 19, 7);
-    style = RInt "index", [String (Device, "device")], [];
-    impl = OCaml "Devsparts.device_index";
-    tests = [
-      InitEmpty, Always, TestResult (
-        [["device_index"; "/dev/sda"]], "ret == 0"), []
-    ];
-    shortdesc = "convert device to index";
-    longdesc = "\
-This function takes a device name (eg. \"/dev/sdb\") and
-returns the index of the device in the list of devices.
-
-Index numbers start from 0.  The named device must exist,
-for example as a string returned from C<guestfs_list_devices>.
-
-See also C<guestfs_list_devices>, C<guestfs_part_to_dev>." };
-
   { defaults with
     name = "nr_devices"; added = (1, 19, 15);
     impl = OCaml "Devsparts.nr_devices";
diff --git a/generator/proc_nr.ml b/generator/proc_nr.ml
index 11a557076..5604662f4 100644
--- a/generator/proc_nr.ml
+++ b/generator/proc_nr.ml
@@ -345,7 +345,6 @@ let proc_nr = [
 332, "btrfs_fsck";
 333, "filesystem_available";
 334, "fstrim";
-335, "device_index";
 336, "nr_devices";
 337, "xfs_info";
 338, "pvchange_uuid";
diff --git a/lib/drives.c b/lib/drives.c
index bba6ff74e..46af66db4 100644
--- a/lib/drives.c
+++ b/lib/drives.c
@@ -1148,3 +1148,21 @@ free_drive_source (struct drive_source *src)
     free_drive_servers (src->servers, src->nr_servers);
   }
 }
+
+int
+guestfs_impl_device_index (guestfs_h *g, const char *device)
+{
+  size_t len;
+  ssize_t r = -1;
+
+  /* /dev/hd etc. */
+  if (STRPREFIX (device, "/dev/") &&
+      strchr (device+5, '/') == NULL && /* not an LV name */
+      device[5] != 'm' && /* not /dev/md - RHBZ#1414682 */
+      ((len = strcspn (device+5, "d")) > 0 && len <= 2))
+    r = guestfs_int_drive_index (device+5+len+1);
+
+  if (r == -1)
+    error (g, _("%s: device not found"), device);
+  return r;
+}