#8735: better explain semantics of *values* argument for parse().
diff --git a/Doc/library/optparse.rst b/Doc/library/optparse.rst
index 37eab37..37226c3 100644
--- a/Doc/library/optparse.rst
+++ b/Doc/library/optparse.rst
@@ -1234,8 +1234,9 @@
the list of arguments to process (default: ``sys.argv[1:]``)
``values``
- object to store option arguments in (default: a new instance of
- :class:`optparse.Values`)
+ a :class:`optparse.Values` object to store option arguments in (default: a
+ new instance of :class:`Values`) -- if you give an existing object, the
+ option defaults will not be initialized on it
and the return values are