diff --git a/tools/lib/test_server.py b/tools/lib/test_server.py
index 9936ea6128..fa61e5e780 100644
--- a/tools/lib/test_server.py
+++ b/tools/lib/test_server.py
@@ -45,7 +45,8 @@ def server_is_up(server, log_file):
     assert_server_running(server, log_file)
     try:
         # We could get a 501 error if the reverse proxy is up but the Django app isn't.
-        return requests.get('http://127.0.0.1:9981/accounts/home').status_code == 200
+        # Note that zulipdev.com is mapped via DNS to 127.0.0.1.
+        return requests.get('http://zulipdev.com:9981/accounts/home').status_code == 200
     except Exception:
         return False