diff --git a/ChangeLog b/ChangeLog
index 65166c5182..d55aa0e606 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Fri Jan 28 11:23:54 2011  KOSAKI Motohiro  <kosaki.motohiro@gmail.com>
+
+	* io.c (rb_io_open): Use NUM2MODET() instead NUM2UINT().
+	* io.c (rb_scan_open_args): ditto.
+
 Fri Jan 28 10:58:20 2011  KOSAKI Motohiro  <kosaki.motohiro@gmail.com>
 
 	* configure.in: Added mode_t type checking.
diff --git a/io.c b/io.c
index eafec788e5..17784588bb 100644
--- a/io.c
+++ b/io.c
@@ -5420,7 +5420,7 @@ rb_scan_open_args(int argc, VALUE *argv,
 
     rb_io_extract_modeenc(&vmode, &vperm, opt, &oflags, &fmode, convconfig_p);
 
-    perm = NIL_P(vperm) ? 0666 :  NUM2UINT(vperm);
+    perm = NIL_P(vperm) ? 0666 :  NUM2MODET(vperm);
 
     *fname_p = fname;
     *oflags_p = oflags;
@@ -5696,7 +5696,7 @@ rb_io_open(VALUE filename, VALUE vmode, VALUE vperm, VALUE opt)
     mode_t perm;
 
     rb_io_extract_modeenc(&vmode, &vperm, opt, &oflags, &fmode, &convconfig);
-    perm = NIL_P(vperm) ? 0666 :  NUM2UINT(vperm);
+    perm = NIL_P(vperm) ? 0666 :  NUM2MODET(vperm);
 
     if (!NIL_P(cmd = check_pipe_command(filename))) {
 	return pipe_open_s(cmd, rb_io_oflags_modestr(oflags), fmode, &convconfig);