diff --git a/ChangeLog b/ChangeLog
index 9e3f5806af..cfea8f3132 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Sun Oct 30 08:29:51 2011  Tanaka Akira  <akr@fsij.org>
+
+	* io.c (rb_cloexec_dup2): don't set CLOEXEC for standard file
+	  descriptors.
+
 Sun Oct 30 07:47:10 2011  Tanaka Akira  <akr@fsij.org>
 
 	* configure.in: check dup3.
diff --git a/io.c b/io.c
index 5bec3622f4..1e04a1d6f5 100644
--- a/io.c
+++ b/io.c
@@ -234,7 +234,7 @@ rb_cloexec_dup2(int oldfd, int newfd)
 
 #if defined(HAVE_DUP3) && defined(O_CLOEXEC)
     static int try_dup3 = 1;
-    if (try_dup3) {
+    if (2 < newfd && try_dup3) {
         ret = dup3(oldfd, newfd, O_CLOEXEC);
         /* dup3 is available since Linux 2.6.27. */
         if (ret == -1 && errno == ENOSYS) {