diff --git a/ChangeLog b/ChangeLog
index 63528e8b9e..abfd3a41f9 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+Tue Feb  1 13:20:39 2011  KOSAKI Motohiro  <kosaki.motohiro@gmail.com>
+
+	* test/benchmark/test_benchmark.rb (#capture_bench_output):
+	  Added explict sleep. Windows have imprecise time support.
+	  Thus Tms.new.Add!{} may be or may be not equal 0. The
+	  test failure started since r30747.
+
 Tue Feb  1 11:03:47 2011  Ryan Davis  <ryan@lust.local>
 
 	* lib/rubygems*: Import rubygems 1.5.0 (released version @ 1fb59d0)
diff --git a/test/benchmark/test_benchmark.rb b/test/benchmark/test_benchmark.rb
index e3305aa0ba..8e369fdb1f 100644
--- a/test/benchmark/test_benchmark.rb
+++ b/test/benchmark/test_benchmark.rb
@@ -123,7 +123,7 @@ describe Benchmark do
     it '[ruby-dev:40906] can add in-place the time of execution of the block given' do
       t = Benchmark::Tms.new
       t.real.must_equal 0
-      t.add! {}
+      t.add! { sleep 0.1 }
       t.real.wont_equal 0
     end
   end