Index: Lib/difflib.py
===================================================================
--- Lib/difflib.py	(revision 54269)
+++ Lib/difflib.py	(working copy)
@@ -313,16 +313,10 @@
                 indices = b2j[elt]
                 if n >= 200 and len(indices) * 100 > n:
                     populardict[elt] = 1
-                    del indices[:]
-                else:
-                    indices.append(i)
+                indices.append(i)
             else:
                 b2j[elt] = [i]
 
-        # Purge leftover indices for popular elements.
-        for elt in populardict:
-            del b2j[elt]
-
         # Now b2j.keys() contains elements uniquely, and especially when
         # the sequence is a string, that's usually a good deal smaller
         # than len(string).  The difference is the number of isjunk calls