diff --git a/Lib/os.py b/Lib/os.py
index 9599cf3..fdb3bed 100644
--- a/Lib/os.py
+++ b/Lib/os.py
@@ -221,7 +221,7 @@
 
 __all__.extend(["makedirs", "removedirs", "renames"])
 
-def walk(top, topdown=True, onerror=None):
+def walk(top, topdown=True, onerror=None, followlinks=False):
     """Directory tree generator.
 
     For each directory in the directory tree rooted at top (including top
@@ -257,6 +257,10 @@
     to abort the walk.  Note that the filename is available as the
     filename attribute of the exception object.
 
+    By default, os.walk does not follow symbolic links to subdirectories on
+    systems that support them.  In order to get this functionality, set the
+    optional argument 'followlinks' to true.
+
     Caution:  if you pass a relative pathname for top, don't change the
     current working directory between resumptions of walk.  walk never
     changes the current directory, and assumes that the client doesn't
@@ -300,8 +304,8 @@
         yield top, dirs, nondirs
     for name in dirs:
         path = join(top, name)
-        if not islink(path):
-            for x in walk(path, topdown, onerror):
+        if followlinks or not islink(path):
+            for x in walk(path, topdown, onerror, followlinks):
                 yield x
     if not topdown:
         yield top, dirs, nondirs