--- a/mercurial/util.py	Mon Nov 29 20:13:11 2010 +0100
+++ b/mercurial/util.py	Tue Nov 30 17:48:12 2010 +0900
@@ -841,7 +841,7 @@
     except OSError, err:
         if err.errno == errno.EEXIST:
             return
-        if err.errno != errno.ENOENT:
+        if not name or err.errno != errno.ENOENT:
             raise
     parent = os.path.abspath(os.path.dirname(name))
     makedirs(parent, mode)