diff --git a/tools/wptserve/wptserve/server.py b/tools/wptserve/wptserve/server.py
index 79140dd54e5c6d..413ae0a8bc9fa5 100644
--- a/tools/wptserve/wptserve/server.py
+++ b/tools/wptserve/wptserve/server.py
@@ -860,7 +860,7 @@ def start(self):
         self.logger.info(f"Starting {http_type} server on {http_scheme}://{self.host}:{self.port}")
         self.started = True
         self.server_thread = threading.Thread(target=self.httpd.serve_forever)
-        self.server_thread.setDaemon(True)  # don't hang on exit
+        self.server_thread.daemon = True  # don't hang on exit
         self.server_thread.start()
 
     def stop(self):