diff --git a/Tools/scripts/run_tests.py b/Tools/scripts/run_tests.py
index bcfa5e9..48feb3f 100644
--- a/Tools/scripts/run_tests.py
+++ b/Tools/scripts/run_tests.py
@@ -25,9 +25,8 @@
             '-u',                 # Unbuffered stdout and stderr
             '-W', 'default',      # Warnings set to 'default'
             '-bb',                # Warnings about bytes/bytearray
+            '-E',                 # Ignore environment variables
             ]
-    if 'PYTHONOLDPARSER' not in os.environ:
-        args.append('-E')         # Ignore environment variables
 
     # Allow user-specified interpreter options to override our defaults.
     args.extend(test.support.args_from_interpreter_flags())