diff --git a/tests/test_activity_monitor.py b/tests/test_activity_monitor.py
index 0398204..56373e3 100644
--- a/tests/test_activity_monitor.py
+++ b/tests/test_activity_monitor.py
@@ -154,6 +154,10 @@ def _queue_stopper() -> None:
         current_io_loop.start()
         stopping_thread.join()
 
+        # cleanly shut down tornado server and loop
+        current_io_loop.close()
+        http_server.stop()
+
     thread = threading.Thread(target=_run_server_worker, daemon=True)
     thread.start()