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 14:25:43 2015 +0200
@@ -2529,9 +2529,9 @@
    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
-   generated before *dirpath* itself is generated.
+   :func:`walk` again.  Modifying *dirnames* when *topdown* is ``False`` has
+   no effect on the behavior of the walk, 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
    argument *onerror* is specified, it should be a function; it will be called with
diff -r bbb4c2c43aea Lib/os.py
--- a/Lib/os.py	Thu Oct 22 22:48:16 2015 -0700
+++ b/Lib/os.py	Fri Oct 23 14:25:43 2015 +0200
@@ -318,10 +318,11 @@
     (e.g., via del or slice assignment), and walk will only recurse into the
     subdirectories whose names remain in dirnames; this can be used to prune the
     search, or to impose a specific order of visiting.  Modifying dirnames when
-    topdown is false is ineffective, since the directories in dirnames have
-    already been generated by the time dirnames itself is generated. No matter
-    the value of topdown, the list of subdirectories is retrieved before the
-    tuples for the directory and its subdirectories are generated.
+    topdown is false has no effect on the behavior of os.walk(), since the 
+    directories in dirnames have already been generated by the time dirnames 
+    itself is generated. No matter the value of topdown, the list of 
+    subdirectories is retrieved before the tuples for the directory and its 
+    subdirectories are generated.
 
     By default errors from the os.scandir() call are ignored.  If
     optional arg 'onerror' is specified, it should be a function; it