diff --git a/ChangeLog b/ChangeLog
index 940453d7d5..9bdc6df386 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Sun Jul 31 18:58:59 2011  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* io.c (rb_pipe): pipe on cygwin can succeed half but fail
+	  half.
+
 Sun Jul 31 11:31:07 2011  Kazuki Tsujimoto  <kazuki@callcc.net>
 
 	* vm.c: check if cfp is valid. [Bug #5083] [ruby-dev:44208]
diff --git a/io.c b/io.c
index 5e52ea6265..6be4e88744 100644
--- a/io.c
+++ b/io.c
@@ -4914,6 +4914,14 @@ rb_pipe(int *pipes)
             ret = pipe(pipes);
         }
     }
+#ifdef __CYGWIN__
+    if (ret == 0 && pipes[1] == -1) {
+	close(pipes[0]);
+	pipes[0] = -1;
+	errno = ENFILE;
+	return -1;
+    }
+#endif
     if (ret == 0) {
         rb_update_max_fd(pipes[0]);
         rb_update_max_fd(pipes[1]);