diff --git a/ChangeLog b/ChangeLog
index 322ddd7d13..4a52a64046 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Sun May 22 20:01:21 2016  Masatoshi SEKI  <m_seki@mva.biglobe.ne.jp>
+
+	* lib/drb/timeridconv.rb: use finalizer trick instead of thread.
+
+	* test/drb/ut_timerholder.rb: ditto.
+
 Sun May 22 17:25:18 2016  Martin Duerst  <duerst@it.aoyama.ac.jp>
 
         * test/ruby/enc/test_case_options.rb: adjust test class name
diff --git a/lib/drb/timeridconv.rb b/lib/drb/timeridconv.rb
index 7e2a6cf998..0f45f4a08e 100644
--- a/lib/drb/timeridconv.rb
+++ b/lib/drb/timeridconv.rb
@@ -24,7 +24,7 @@ module DRb
         @gc = {}
         @renew = {}
         @keeping = keeping
-        @expires = Time.now + @keeping
+        @expires = nil
       end
 
       def add(obj)
@@ -32,18 +32,16 @@ module DRb
           rotate
           key = obj.__id__
           @renew[key] = obj
+          invoke_keeper
           return key
         end
       end
 
-      def fetch(key, dv=@sentinel)
+      def fetch(key)
         synchronize do
           rotate
           obj = peek(key)
-          if obj == @sentinel
-            return dv unless dv == @sentinel
-            raise InvalidIndexError
-          end
+          raise InvalidIndexError if obj == @sentinel
           @renew[key] = obj # KeepIt
           return obj
         end
@@ -51,25 +49,28 @@ module DRb
 
       private
       def peek(key)
-        synchronize do
-          return @renew.fetch(key) { @gc.fetch(key, @sentinel) }
-        end
+        return @renew.fetch(key) { @gc.fetch(key, @sentinel) }
+      end
+
+      def invoke_keeper
+        return if @expires
+        @expires = Time.now + @keeping
+        on_gc
+      end
+
+      def on_gc
+        return unless Thread.main.alive?
+        return if @expires.nil?
+        Thread.new { rotate } if @expires < Time.now
+        ObjectSpace.define_finalizer(Object.new) {on_gc}          
       end
 
       def rotate
         synchronize do
-          return if @expires > Time.now
-          @gc = @renew      # GCed
-          @renew = {}
-          @expires = Time.now + @keeping
-        end
-      end
-
-      def keeper
-        Thread.new do
-          loop do
-            rotate
-            sleep(@keeping)
+          if @expires &.< Time.now
+            @gc = @renew      # GCed
+            @renew = {}
+            @expires = @gc.empty? ? nil : Time.now + @keeping
           end
         end
       end
diff --git a/test/drb/ut_timerholder.rb b/test/drb/ut_timerholder.rb
index 252c7bd228..1753b30c74 100644
--- a/test/drb/ut_timerholder.rb
+++ b/test/drb/ut_timerholder.rb
@@ -12,7 +12,6 @@ class TimerIdConvTest < Test::Unit::TestCase
     key = idconv.to_id(self)
     assert_equal(key, self.__id__)
     sleep(keeping)
-
     assert_equal(idconv.to_id(false), false.__id__)
     assert_equal(idconv.to_obj(key), self)
     sleep(keeping)
@@ -24,11 +23,48 @@ class TimerIdConvTest < Test::Unit::TestCase
     sleep(keeping)
 
     assert_raise do
-      assert_equal(idconv.to_obj(key))
+      assert_equal(idconv.to_obj(key), self)
     end
 
     assert_raise do
-      assert_equal(idconv.to_obj(false.__id__))
+      assert_equal(idconv.to_obj(false.__id__), false)
+    end
+
+    key = idconv.to_id(self)
+    assert_equal(key, self.__id__)
+    assert_equal(idconv.to_id(true), true.__id__)
+    sleep(keeping)
+    GC.start
+    sleep(keeping)
+    GC.start
+    assert_raise do
+      assert_equal(idconv.to_obj(key), self)
+    end
+  end
+
+  def test_usecase_02
+    keeping = 0.1
+    idconv = DRb::TimerIdConv.new(keeping)
+
+    key = idconv.to_id(self)
+    assert_equal(key, self.__id__)
+    sleep(keeping)
+    GC.start
+    sleep(keeping)
+    GC.start
+    assert_raise do
+      assert_equal(idconv.to_obj(key), self)
+    end
+    GC.start
+
+    key = idconv.to_id(self)
+    assert_equal(key, self.__id__)
+    sleep(keeping)
+    GC.start
+    sleep(keeping)
+    GC.start
+    assert_raise do
+      assert_equal(idconv.to_obj(key), self)
     end
   end
 end