Issue #13140: Fix the daemon_threads attribute of ThreadingMixIn.
diff --git a/Lib/SocketServer.py b/Lib/SocketServer.py
index 71b9caa..2ff3888 100644
--- a/Lib/SocketServer.py
+++ b/Lib/SocketServer.py
@@ -589,8 +589,7 @@
         """Start a new thread to process the request."""
         t = threading.Thread(target = self.process_request_thread,
                              args = (request, client_address))
-        if self.daemon_threads:
-            t.setDaemon (1)
+        t.daemon = self.daemon_threads
         t.start()