diff --git a/test/test_supervisor.rb b/test/test_supervisor.rb
index 2ad47a4070..51c344e669 100644
--- a/test/test_supervisor.rb
+++ b/test/test_supervisor.rb
@@ -264,6 +264,9 @@ def test_usr1_in_main_process_signal_handlers
   def test_cont_in_main_process_signal_handlers
     omit "Windows cannot handle signals" if Fluent.windows?
 
+    # https://github.com/fluent/fluentd/issues/4063
+    GC.start
+
     sv = Fluent::Supervisor.new({})
     sv.send(:install_main_process_signal_handlers)
 
@@ -279,6 +282,9 @@ def test_cont_in_main_process_signal_handlers
   def test_term_cont_in_main_process_signal_handlers
     omit "Windows cannot handle signals" if Fluent.windows?
 
+    # https://github.com/fluent/fluentd/issues/4063
+    GC.start
+
     create_debug_dummy_logger
 
     sv = Fluent::Supervisor.new({})
@@ -365,6 +371,9 @@ def test_usr1_in_supervisor_signal_handler
   def test_cont_in_supervisor_signal_handler
     omit "Windows cannot handle signals" if Fluent.windows?
 
+    # https://github.com/fluent/fluentd/issues/4063
+    GC.start
+
     server = DummyServer.new
     server.install_supervisor_signal_handlers
 
@@ -380,6 +389,9 @@ def test_cont_in_supervisor_signal_handler
   def test_term_cont_in_supervisor_signal_handler
     omit "Windows cannot handle signals" if Fluent.windows?
 
+    # https://github.com/fluent/fluentd/issues/4063
+    GC.start
+
     server = DummyServer.new
     server.install_supervisor_signal_handlers