diff --git a/ChangeLog b/ChangeLog
index ead7f5dbff..5ff01b2977 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Mon Jan 25 21:43:05 2010  Yusuke Endoh  <mame@tsg.ne.jp>
+
+	* test/ruby/envutil.rb: fix the check if instance method `ruby' is
+	  defined or not.
+
 Mon Jan 25 21:17:32 2010  Yusuke Endoh  <mame@tsg.ne.jp>
 
 	* test/ruby/test_rubyoptions.rb (test_segv_test): add a test for
diff --git a/test/ruby/envutil.rb b/test/ruby/envutil.rb
index 741aa75ce3..1d9c4f6990 100644
--- a/test/ruby/envutil.rb
+++ b/test/ruby/envutil.rb
@@ -208,7 +208,7 @@ else
   module RbConfig
     @ruby = EnvUtil.rubybin
     class << self
-      undef ruby if defined?(ruby)
+      undef ruby if instance_methods.include?(:ruby)
       attr_reader :ruby
     end
     dir = File.dirname(ruby)