Index: Modules/unicodedata.c
===================================================================
--- Modules/unicodedata.c	(révision 72267)
+++ Modules/unicodedata.c	(copie de travail)
@@ -682,7 +682,7 @@
       comb = 0;
       while (i1 < end) {
           int comb1 = _getrecord_ex(*i1)->combining;
-          if (comb1 && comb == comb1) {
+          if (comb && (comb1 == 0 || comb == comb1)) {
               /* Character is blocked. */
               i1++;
               continue;
Index: Lib/test/test_unicodedata.py
===================================================================
--- Lib/test/test_unicodedata.py	(révision 72267)
+++ Lib/test/test_unicodedata.py	(copie de travail)
@@ -185,6 +185,11 @@
         # The rest can be found in test_normalization.py
         # which requires an external file.
 
+    def test_pr29(self):
+        # http://www.unicode.org/review/pr-29.html
+        for text in (u"\u0b47\u0300\u0b3e", u"\u1100\u0300\u1161"):
+            self.assertEqual(self.db.normalize('NFC', text), text)
+
     def test_east_asian_width(self):
         eaw = self.db.east_asian_width
         self.assertRaises(TypeError, eaw, 'a')