diff --git a/ChangeLog b/ChangeLog
index 975195967a..ae163edd20 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Sat Aug 25 10:05:17 2007  Koichi Sasada  <ko1@atdot.net>
+
+	* prelude.rb: add Thread.exclusive.  This class method
+	  is different from 1.8's.  Thread.exclusive only does
+	  synchronize with VM global mutex.
+
 Sat Aug 25 09:39:50 2007  Yukihiro Matsumoto  <matz@ruby-lang.org>
 
 	* array.c (rb_ary_s_try_convert): more document description.
diff --git a/prelude.rb b/prelude.rb
index 6451b8f74a..8ce306caa2 100644
--- a/prelude.rb
+++ b/prelude.rb
@@ -10,3 +10,14 @@ class Mutex
   end
 end
 
+# Thread
+
+class Thread
+  MUTEX_FOR_THREAD_EXCLUSIVE = Mutex.new
+  def self.exclusive
+    MUTEX_FOR_THREAD_EXCLUSIVE.synchronize{
+      yield
+    }
+  end
+end
+