diff --git a/pep-0657.rst b/pep-0657.rst
index 2283f3cf1..e161deb55 100644
--- a/pep-0657.rst
+++ b/pep-0657.rst
@@ -321,7 +321,7 @@ programs that are currently parsing tracebacks to catch up the following
 methods will be provided to deactivate this feature:
 
 * A new environment variable: ``PYTHONNODEBUGRANGES``.
-* A new command line option for the dev mode: ``python -Xnodebugranges``.
+* A new command line option for the dev mode: ``python -Xno_debug_ranges``.
 
 If any of these methods are used, the Python compiler will **not** populate
 code objects with the new information (``None`` will be used instead) and any