diff --git a/ChangeLog b/ChangeLog
index c82bf40e68..8760f5b29b 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Tue Feb  8 16:04:03 2011  KOSAKI Motohiro  <kosaki.motohiro@gmail.com>
+
+	* io.c (rb_io_s_sysopen): use NUM2MODET() instead NUM2UINT().
+
 Tue Feb  8 15:59:23 2011  KOSAKI Motohiro  <kosaki.motohiro@gmail.com>
 
 	* process.c (rb_run_exec_options_err): use MODET2NUM() instead LONG2NUM().
diff --git a/io.c b/io.c
index 89932953ef..a50159771c 100644
--- a/io.c
+++ b/io.c
@@ -5521,7 +5521,7 @@ rb_io_s_sysopen(int argc, VALUE *argv)
 	oflags = rb_io_modestr_oflags(StringValueCStr(vmode));
     }
     if (NIL_P(vperm)) perm = 0666;
-    else              perm = NUM2UINT(vperm);
+    else              perm = NUM2MODET(vperm);
 
     RB_GC_GUARD(fname) = rb_str_new4(fname);
     fd = rb_sysopen(fname, oflags, perm);