diff --git a/ChangeLog b/ChangeLog
index 126ca60ad9..33f6263a21 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,4 +1,8 @@
-Wed Nov  9 22:54:30 2011  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+Wed Nov  9 23:20:22 2011  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* io.c (rb_update_max_fd): fstat(2) can fail with other than
+	  EBADF.  [ruby-dev:44837] [Backport #4339].  Cf.
+	  http://pubs.opengroup.org/onlinepubs/9699919799/functions/fstat.html
 
 	* io.c (rb_sysopen): max fd is updated in rb_sysopen_internal()
 	  already.
diff --git a/io.c b/io.c
index 0ffeb85942..bc661ce6d2 100644
--- a/io.c
+++ b/io.c
@@ -151,7 +151,7 @@ void
 rb_update_max_fd(int fd)
 {
     struct stat buf;
-    if (fstat(fd, &buf) != 0) {
+    if (fstat(fd, &buf) != 0 && errno == EBADF) {
         rb_bug("rb_update_max_fd: invalid fd (%d) given.", fd);
     }
     if (max_file_descriptor < fd) max_file_descriptor = fd;