diff --git a/ChangeLog b/ChangeLog
index b2e5ab3b85..894e5e6ea3 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Sat Jun 20 07:17:52 2009  Yukihiro Matsumoto  <matz@ruby-lang.org>
+
+	* lib/monitor.rb (MonitorMixin::extend_object): should use
+	  #__send__ instead of #send to avoid possible name conflict.  
+	  [ruby-core:23907]
+
 Sat Jun 20 06:56:31 2009  Tadayoshi Funaba  <tadf@dotrb.org>
 
 	* complex.c: edited rdoc.
diff --git a/lib/monitor.rb b/lib/monitor.rb
index 00d85fae52..b9bf28ded0 100644
--- a/lib/monitor.rb
+++ b/lib/monitor.rb
@@ -91,13 +91,13 @@ module MonitorMixin
       if timeout
         raise NotImplementedError, "timeout is not implemented yet"
       end
-      @monitor.send(:mon_check_owner)
-      count = @monitor.send(:mon_exit_for_cond)
+      @monitor.__send__(:mon_check_owner)
+      count = @monitor.__send__(:mon_exit_for_cond)
       begin
         @cond.wait(@monitor.instance_variable_get("@mon_mutex"))
         return true
       ensure
-        @monitor.send(:mon_enter_for_cond, count)
+        @monitor.__send__(:mon_enter_for_cond, count)
       end
     end
 
@@ -114,12 +114,12 @@ module MonitorMixin
     end
 
     def signal
-      @monitor.send(:mon_check_owner)
+      @monitor.__send__(:mon_check_owner)
       @cond.signal
     end
 
     def broadcast
-      @monitor.send(:mon_check_owner)
+      @monitor.__send__(:mon_check_owner)
       @cond.broadcast
     end
 
@@ -137,7 +137,7 @@ module MonitorMixin
 
   def self.extend_object(obj)
     super(obj)
-    obj.send(:mon_initialize)
+    obj.__send__(:mon_initialize)
   end
 
   #