diff -r 7bff23ec3f5b Lib/test/test_unicode.py
--- a/Lib/test/test_unicode.py	Sun Jul 17 10:13:44 2011 -0400
+++ b/Lib/test/test_unicode.py	Sun Jul 17 10:38:18 2011 -0400
@@ -736,6 +736,9 @@
         self.assertRaises(TypeError, '{a'.format_map)
         self.assertRaises(TypeError, '}a'.format_map)
 
+        # test non-mapping error
+        self.assertRaises(TypeError, '{}'.format_map, "a")
+
     def test_format_auto_numbering(self):
         class C:
             def __init__(self, x=100):