diff --git a/ChangeLog b/ChangeLog
index 70c1183c34..c4d2ac553c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Fri Jul 23 16:07:32 2010  Shugo Maeda  <shugo@ruby-lang.org>
+
+	* lib/mutex_m.rb (sleep): added Mutex_m#sleep to support
+	  ConditionVariable.
+
 Fri Jul 23 15:09:22 2010  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* configure.in (RUBY_MINGW32): ignore msvc suffix.
diff --git a/lib/mutex_m.rb b/lib/mutex_m.rb
index 081bb788e4..b9937b635d 100644
--- a/lib/mutex_m.rb
+++ b/lib/mutex_m.rb
@@ -78,6 +78,10 @@ module Mutex_m
     @_mutex.unlock
   end
 
+  def sleep(timeout = nil)
+    @_mutex.sleep(timeout)
+  end
+
   private
 
   def mu_initialize
diff --git a/test/test_mutex_m.rb b/test/test_mutex_m.rb
new file mode 100644
index 0000000000..ab8927dd0f
--- /dev/null
+++ b/test/test_mutex_m.rb
@@ -0,0 +1,25 @@
+require 'test/unit'
+require 'thread'
+require 'mutex_m'
+
+class TestMutexM < Test::Unit::TestCase
+  def test_cv_wait
+    o = Object.new
+    o.extend(Mutex_m)
+    c = ConditionVariable.new
+    t = Thread.start {
+      o.synchronize do
+        until foo = o.instance_variable_get(:@foo)
+          c.wait(o)
+        end
+        foo
+      end
+    }
+    sleep(0.0001)
+    o.synchronize do
+      o.instance_variable_set(:@foo, "abc")
+    end
+    c.signal
+    assert_equal "abc", t.value
+  end
+end