diff --git a/ocamltest/main.ml b/ocamltest/main.ml
index 12b0c06c0..9197ce325 100644
--- a/ocamltest/main.ml
+++ b/ocamltest/main.ml
@@ -152,9 +152,9 @@ let test_file test_filename =
   let test_build_directory_prefix =
     get_test_build_directory_prefix test_directory in
   let clean_test_build_directory () =
-    ignore
-      (Sys.command
-         (Filename.quote_command "rm" ["-rf"; test_build_directory_prefix]))
+    try
+      Sys.rm_rf test_build_directory_prefix
+    with Sys_error _ -> ()
   in
   clean_test_build_directory ();
   Sys.make_directory test_build_directory_prefix;
diff --git a/ocamltest/ocamltest_stdlib.ml b/ocamltest/ocamltest_stdlib.ml
index a95dd3dc5..07d69889a 100644
--- a/ocamltest/ocamltest_stdlib.ml
+++ b/ocamltest/ocamltest_stdlib.ml
@@ -86,6 +86,25 @@ end
 module Sys = struct
   include Sys
 
+  let erase_file path =
+    try Sys.remove path
+    with Sys_error _ when Sys.win32 && Ocamltest_config.libunix <> None ->
+      (* Deal with read-only attribute on Windows. Ignore any error from chmod
+         so that the message always come from Sys.remove *)
+      let () = try Unix.chmod path 0o666 with Sys_error _ -> () in
+      Sys.remove path
+
+  let rm_rf path =
+    let rec erase path =
+      if Sys.is_directory path
+      then Array.iter (fun entry -> erase (Filename.concat path entry))
+                      (Sys.readdir path)
+      else erase_file path
+    in
+      try if Sys.file_exists path then erase path
+      with Sys_error err ->
+        raise (Sys_error (Printf.sprintf "Failed to remove %S (%s)" path err))
+
   let run_system_command prog args =
     let command = Filename.quote_command prog args in
     match Sys.command command with
diff --git a/ocamltest/ocamltest_stdlib.mli b/ocamltest/ocamltest_stdlib.mli
index 8ab88d663..d19147f9b 100644
--- a/ocamltest/ocamltest_stdlib.mli
+++ b/ocamltest/ocamltest_stdlib.mli
@@ -48,6 +48,7 @@ module Sys : sig
   val file_is_empty : string -> bool
   val run_system_command : string -> string list -> unit
   val make_directory : string -> unit
+  val rm_rf : string -> unit
   val string_of_file : string -> string
   val iter_lines_of_file : (string -> unit) -> string -> unit
   val dump_file : out_channel -> ?prefix:string -> string -> unit
diff --git a/ocamltest/ocamltest_unix.mli b/ocamltest/ocamltest_unix.mli
index ed952213f..38d1883eb 100644
--- a/ocamltest/ocamltest_unix.mli
+++ b/ocamltest/ocamltest_unix.mli
@@ -16,3 +16,4 @@
     temptation to use the Unix module directly in ocamltest. *)
 
 val has_symlink : unit -> bool
+val chmod : string -> int -> unit
diff --git a/ocamltest/ocamltest_unix_dummy.ml b/ocamltest/ocamltest_unix_dummy.ml
index 1a079cf7b..207cc716d 100644
--- a/ocamltest/ocamltest_unix_dummy.ml
+++ b/ocamltest/ocamltest_unix_dummy.ml
@@ -14,3 +14,4 @@
 
 (* Dummy implementations for when the Unix library isn't built *)
 let has_symlink () = false
+let chmod _ _ = invalid_arg "chmod not available"
diff --git a/ocamltest/ocamltest_unix_real.ml b/ocamltest/ocamltest_unix_real.ml
index 68cfbb2e0..2a63e8bbb 100644
--- a/ocamltest/ocamltest_unix_real.ml
+++ b/ocamltest/ocamltest_unix_real.ml
@@ -12,6 +12,17 @@
 (*                                                                        *)
 (**************************************************************************)
 
-(* It's tempting just to have include Unix, but the binary is then quite a bit
-   bigger. *)
+(* Unix.has_symlink never raises *)
 let has_symlink = Unix.has_symlink
+
+(* Convert Unix_error to Sys_error *)
+let wrap f x =
+  try f x
+  with Unix.Unix_error(err, fn_name, arg) ->
+    let msg =
+      Printf.sprintf "%s failed on %S with %s"
+                     fn_name arg (Unix.error_message err)
+    in
+      raise (Sys_error msg)
+
+let chmod file = wrap (Unix.chmod file)