diff --git a/zeroconf.py b/zeroconf.py
index 2d67563e..ac363008 100644
--- a/zeroconf.py
+++ b/zeroconf.py
@@ -1038,6 +1038,7 @@ def enqueue_callback(state_change, name):
     def cancel(self):
         self.done = True
         self.zc.notify_all()
+        self.join()
 
     def run(self):
         while True:
@@ -1675,5 +1676,7 @@ def close(self):
             self.notify_all()
             self.engine.notify()
             self.unregister_all_services()
+            self.reaper.join()
+            self.engine.join()
             for s in [self._listen_socket] + self._respond_sockets:
                 s.close()