diff --git a/ChangeLog b/ChangeLog
index cf283ab3ae..46f8d613b0 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Sat Jul  9 08:37:05 2011  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* io.c (rb_io_close): close(2) on a fd which is being read by
+	  another thread causes deadlock on Mac OS X 10.5
+
 Fri Jul  8 21:20:39 2011  NARUSE, Yui  <naruse@ruby-lang.org>
 
 	* addr2line.c: use USE_ELF instead of __ELF__ because Solaris
diff --git a/io.c b/io.c
index e5372aa820..90cc2b3a30 100644
--- a/io.c
+++ b/io.c
@@ -3621,6 +3621,12 @@ rb_io_close(VALUE io)
     if (fptr->fd < 0) return Qnil;
 
     fd = fptr->fd;
+#if defined __APPLE__ && defined(__MACH__) && \
+    (!defined(MAC_OS_X_VERSION_MIN_ALLOWED) || MAC_OS_X_VERSION_MIN_ALLOWED <= 1050)
+    /* close(2) on a fd which is being read by another thread causes
+     * deadlock on Mac OS X 10.5 */
+    rb_thread_fd_close(fd);
+#endif
     rb_io_fptr_cleanup(fptr, FALSE);
     rb_thread_fd_close(fd);