diff -r b8a6bc70fc08 Lib/test/test_unicode.py
--- a/Lib/test/test_unicode.py	Thu Feb 07 17:05:32 2013 +0200
+++ b/Lib/test/test_unicode.py	Thu Feb 07 17:15:48 2013 +0100
@@ -7,6 +7,7 @@ Written by Marc-Andre Lemburg (mal@lembu
 """#"
 import _string
 import codecs
+import random
 import struct
 import sys
 import unittest
@@ -2191,6 +2192,20 @@ class UnicodeTest(string_tests.CommonTes
         self.assertEqual(args[0], text)
         self.assertEqual(len(args), 1)
 
+    def test_resize(self):
+        for length in range(1, 100, 7):
+            # generate a fresh string (refcount=1)
+            text = 'a' * length + 'b'
+
+            # fill wstr internal field
+            abc = text.encode('unicode_internal')
+            self.assertEqual(abc.decode('unicode_internal'), text)
+
+            text += 'c'
+            abcdef = text.encode('unicode_internal')
+            self.assertNotEqual(abc, abcdef)
+            self.assertEqual(abcdef.decode('unicode_internal'), text)
+
 
 class StringModuleTest(unittest.TestCase):
     def test_formatter_parser(self):
diff -r b8a6bc70fc08 Objects/unicodeobject.c
--- a/Objects/unicodeobject.c	Thu Feb 07 17:05:32 2013 +0200
+++ b/Objects/unicodeobject.c	Thu Feb 07 17:15:48 2013 +0100
@@ -717,6 +717,10 @@ resize_compact(PyObject *unicode, Py_ssi
         if (!PyUnicode_IS_ASCII(unicode))
             _PyUnicode_WSTR_LENGTH(unicode) = length;
     }
+    else if (_PyUnicode_HAS_WSTR_MEMORY(unicode)) {
+        PyObject_DEL(_PyUnicode_WSTR(unicode));
+        _PyUnicode_WSTR(unicode) = NULL;
+    }
 #ifdef Py_DEBUG
     unicode_fill_invalid(unicode, old_length);
 #endif