diff --git a/reflex/testing.py b/reflex/testing.py
index d0c6a32d3d8..973bc75654d 100644
--- a/reflex/testing.py
+++ b/reflex/testing.py
@@ -14,6 +14,7 @@
 import socket
 import socketserver
 import subprocess
+import sys
 import textwrap
 import threading
 import time
@@ -470,7 +471,7 @@ def stop(self) -> None:
             frontend_children = psutil.Process(self.frontend_process.pid).children(
                 recursive=True,
             )
-            if platform.system() == "Windows":
+            if sys.platform == "win32":
                 self.frontend_process.terminate()
             else:
                 pgrp = os.getpgid(self.frontend_process.pid)