diff --git a/spine_engine/server/engine_server.py b/spine_engine/server/engine_server.py
index 21c9c70..9ef1956 100644
--- a/spine_engine/server/engine_server.py
+++ b/spine_engine/server/engine_server.py
@@ -83,7 +83,7 @@ def close(self):
         """Closes the server by sending a KILL message to this thread using a PAIR socket."""
         if self.auth is not None:
             self.auth.stop()
-            time.sleep(0.2)  # wait a bit until authenticator has been closed
+            self.auth.thread.join()
         self.ctrl_msg_sender.send(b"KILL")
         self.join()  # Wait for the thread to finish and sockets to close
         self.ctrl_msg_sender.close()  # Close this in the same thread that it was created in