diff --git a/lib/drb/drb.rb b/lib/drb/drb.rb
index 4c0f396d44..e2aaf701ce 100644
--- a/lib/drb/drb.rb
+++ b/lib/drb/drb.rb
@@ -1215,6 +1215,7 @@ module DRb
 
     def kill
       @thread.kill
+      @thread.join
     end
 
     def method_missing(msg, *arg, &blk)
diff --git a/test/drb/drbtest.rb b/test/drb/drbtest.rb
index e292cbfb0d..a8363b0c43 100644
--- a/test/drb/drbtest.rb
+++ b/test/drb/drbtest.rb
@@ -42,6 +42,7 @@ class DRbService
     server.stop_service
     manager.instance_variable_get(:@queue)&.push(nil)
     manager.instance_variable_get(:@thread)&.join
+    DRb::DRbConn.stop_pool
   end
 end
 
diff --git a/test/drb/test_drb.rb b/test/drb/test_drb.rb
index 9242a22543..b792349f28 100644
--- a/test/drb/test_drb.rb
+++ b/test/drb/test_drb.rb
@@ -329,6 +329,7 @@ class TestDRbAnyToS < Test::Unit::TestCase
     assert_match(/\A#<DRbTests::TestDRbAnyToS::BO:0x[0-9a-f]+>\z/, server.any_to_s(BO.new))
     server.stop_service
     server.thread.join
+    DRb::DRbConn.stop_pool
   end
 end
 
@@ -344,6 +345,7 @@ class TestDRbTCP < Test::Unit::TestCase
     client.close
     server.stop_service
     server.thread.join
+    DRb::DRbConn.stop_pool
   end
 end
 
diff --git a/test/drb/test_drbobject.rb b/test/drb/test_drbobject.rb
index 16b252d3ce..2b0e2061ee 100644
--- a/test/drb/test_drbobject.rb
+++ b/test/drb/test_drbobject.rb
@@ -12,6 +12,7 @@ module DRbObjectTest
 
   def teardown
     DRb.stop_service
+    DRb::DRbConn.stop_pool
   end
 
   def drb_eq(obj)
@@ -43,7 +44,19 @@ class TestDRbObjectTimerIdConv < Test::Unit::TestCase
   include DRbObjectTest
 
   def setup
-    DRb.start_service(nil, nil, {:idconv => DRb::TimerIdConv.new})
+    @idconv = DRb::TimerIdConv.new
+    DRb.start_service(nil, nil, {:idconv => @idconv})
+  end
+
+  def teardown
+    super
+    # stop DRb::TimerIdConv::TimerHolder2#on_gc
+    @idconv.instance_eval do
+      @holder.instance_eval do
+        @expires = nil
+      end
+    end
+    GC.start
   end
 end