diff --git a/ChangeLog b/ChangeLog
index bfc60af5c8..f52793e0a7 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Tue Nov  2 20:10:32 2010  Tajima Akio <artonx@yahoo.co.jp>
+
+	* test/rake/test_tasks.rb: clear env var which is used by the test.
+	  [ruby-dev:42508]
+
 Tue Nov  2 00:25:54 2010  NAKAMURA Usaku  <usa@ruby-lang.org>
 
 	* ext/socket/extconf.rb: win64 is just same with win32 about socket.
diff --git a/test/rake/test_tasks.rb b/test/rake/test_tasks.rb
index a042ec4fc2..110ee26a9e 100644
--- a/test/rake/test_tasks.rb
+++ b/test/rake/test_tasks.rb
@@ -305,6 +305,7 @@ class Rake::TestTaskWithArguments < Test::Unit::TestCase
   end
 
   def test_extra_parameters_are_ignored
+    ENV['b'] = nil
     t = task(:t, :a) { |tt, args|
       assert_equal 1, args.a
       assert_nil args.b