diff --git a/Doc/using/cmdline.rst b/Doc/using/cmdline.rst
--- a/Doc/using/cmdline.rst
+++ b/Doc/using/cmdline.rst
@@ -210,9 +210,9 @@
 
 .. cmdoption:: -O
 
-   Turn on basic optimizations.  This changes the filename extension for
-   compiled (:term:`bytecode`) files from ``.pyc`` to ``.pyo``.  See also
-   :envvar:`PYTHONOPTIMIZE`.
+   Removes assert statements and any code conditional on the value of __debug__.
+   This changes the filename extension for compiled (:term:`bytecode`) files
+   from ``.pyc`` to ``.pyo``.  See also :envvar:`PYTHONOPTIMIZE`.
 
 
 .. cmdoption:: -OO