diff --git a/ChangeLog b/ChangeLog
index 83ffc91bd2..d85932fd36 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+Sat Apr  3 03:19:01 2010  Kazuhiro NISHIYAMA  <zn@mbf.nifty.com>
+
+	* lib/benchmark.rb (Benchmark::Tms#add): fix NameError.
+	  [ruby-dev:40906]
+
+	* test/benchmark/test_benchmark.rb: add a test for above.
+
 Sat Apr  3 01:50:02 2010  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* lib/rdoc/parser/ruby.rb (RDoc#make_message): no empty lines.
diff --git a/lib/benchmark.rb b/lib/benchmark.rb
index 9a0bbef596..8e7f778e2d 100644
--- a/lib/benchmark.rb
+++ b/lib/benchmark.rb
@@ -440,7 +440,7 @@ module Benchmark
     #
     # An in-place version of #add.
     #
-    def add!
+    def add!(&blk)
       t = Benchmark::measure(&blk)
       @utime  = utime + t.utime
       @stime  = stime + t.stime
diff --git a/test/benchmark/test_benchmark.rb b/test/benchmark/test_benchmark.rb
new file mode 100644
index 0000000000..6d390558ac
--- /dev/null
+++ b/test/benchmark/test_benchmark.rb
@@ -0,0 +1,10 @@
+require "test/unit"
+require "benchmark"
+
+class TestBenchmark < Test::Unit::TestCase
+  def test_add!
+    assert_nothing_raised("[ruby-dev:40906]") do
+      Benchmark::Tms.new.add! {}
+    end
+  end
+end