diff --git a/pylib/gyp/common_test.py b/pylib/gyp/common_test.py
index 30678e1e..01d1987e 100755
--- a/pylib/gyp/common_test.py
+++ b/pylib/gyp/common_test.py
@@ -111,7 +111,7 @@ def mock_run(env, defines_stdout, expected_cmd):
                             "-dM", "-E", "-x", "c", expected_input
                         ],
                         shell=sys.platform == "win32",
-                        stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
+                        stdout=subprocess.PIPE, stderr=subprocess.PIPE)
                 return [defines, flavor]
 
         [defines1, _] = mock_run({}, "", [])