Index: Lib/urllib2.py
===================================================================
--- Lib/urllib2.py	(revision 77066)
+++ Lib/urllib2.py	(working copy)
@@ -1072,9 +1072,8 @@
                 request.add_unredirected_header(
                     'Content-type',
                     'application/x-www-form-urlencoded')
-            if not request.has_header('Content-length'):
-                request.add_unredirected_header(
-                    'Content-length', '%d' % len(data))
+            request.add_unredirected_header('Content-length',
+                                            '%d' % len(data))
 
         sel_host = host
         if request.has_proxy():