diff --git a/ChangeLog b/ChangeLog
index 0c1bfecd1c..896ad45264 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Fri Sep 14 00:34:25 2007  Masatoshi SEKI  <m_seki@mva.biglobe.ne.jp>
+
+	* lib/drb/extservm.rb (invoke_service): use Thread.exclusive instead of 
+	  Thread.critical
+
 Wed Sep 12 23:12:22 2007  Yukihiro Matsumoto  <matz@ruby-lang.org>
 
 	* ruby.c (proc_options): -W should be allowed in RUBYOPT
diff --git a/lib/drb/extservm.rb b/lib/drb/extservm.rb
index 7066f84c65..91cbc3180f 100644
--- a/lib/drb/extservm.rb
+++ b/lib/drb/extservm.rb
@@ -73,10 +73,11 @@ module DRb
     end
 
     def invoke_service(name)
-      Thread.critical = true
-      @waiting.push Thread.current
-      @queue.push name
-      Thread.stop
+      Thread.exclusive do
+        @waiting.push Thread.current
+        @queue.push name
+        Thread.stop
+      end
     end
 
     def invoke_service_command(name, command)