diff --git a/Lib/distutils/dir_util.py b/Lib/distutils/dir_util.py
index c049bbd..194183a 100644
--- a/Lib/distutils/dir_util.py
+++ b/Lib/distutils/dir_util.py
@@ -7,7 +7,8 @@
 __revision__ = "$Id$"
 
 import os
-from distutils.errors import DistutilsFileError
+from types import *
+from distutils.errors import DistutilsFileError, DistutilsInternalError
 
 
 # cache for by mkpath() -- in addition to cheapening redundant calls,
@@ -29,6 +30,11 @@
 
     global PATH_CREATED
 
+    # Detect a common bug -- name is None
+    if type(name) is not StringType:
+        raise DistutilsInternalError, \
+              "mkpath: 'name' must be a string (got %s)" % `name`
+
     # XXX what's the better way to handle verbosity? print as we create
     # each directory in the path (the current behaviour), or only announce
     # the creation of the whole path? (quite easy to do the latter since