diff -r bbb4c2c43aea Doc/library/os.rst
--- a/Doc/library/os.rst	Thu Oct 22 22:48:16 2015 -0700
+++ b/Doc/library/os.rst	Fri Oct 23 11:35:04 2015 +0200
@@ -2529,8 +2529,8 @@
    recurse into the subdirectories whose names remain in *dirnames*; this can be
    used to prune the search, impose a specific order of visiting, or even to inform
    :func:`walk` about directories the caller creates or renames before it resumes
-   :func:`walk` again.  Modifying *dirnames* when *topdown* is ``False`` is
-   ineffective, because in bottom-up mode the directories in *dirnames* are
+   :func:`walk` again.  Modifying *dirnames* when *topdown* is ``False`` has
+   no effect, because in bottom-up mode the directories in *dirnames* are
    generated before *dirpath* itself is generated.
 
    By default, errors from the :func:`listdir` call are ignored.  If optional