diff --git a/ChangeLog b/ChangeLog
index e828198b41..9e24905633 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,4 +1,7 @@
-Tue May  8 03:54:34 2012  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+Tue May  8 04:47:44 2012  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* lib/test/unit.rb (Test::Unit::Runner#output): prefer local output to
+	  get rid of unexpected side effect in test/minitest/metametameta.rb.
 
 	* lib/test/unit.rb (MiniTest#run_test): show the running test in $0.
 
diff --git a/lib/test/unit.rb b/lib/test/unit.rb
index 90b957512e..2d25f2f2c3 100644
--- a/lib/test/unit.rb
+++ b/lib/test/unit.rb
@@ -655,10 +655,14 @@ module Test
 
       alias mini_run_suite _run_suite
 
+      def output
+        @output || super
+      end
+
       def _prepare_run(suites, type)
         if @tty
           @verbose ||= !options[:parallel]
-          MiniTest::Unit.output = StatusLineOutput.new(self)
+          @output = StatusLineOutput.new(self)
         end
         if /\A\/(.*)\/\z/ =~ (filter = options[:filter])
           options[:filter] = filter = Regexp.new($1)