diff -r 07200e3332a1 -r f2fd087a75ef mercurial/parsers.c
--- a/mercurial/parsers.c	Wed Apr 15 17:42:38 2015 -0400
+++ b/mercurial/parsers.c	Wed Apr 15 14:35:44 2015 -0700
@@ -205,7 +205,20 @@
 		goto quit;
 	}
 
+#if PY_VERSION_HEX >= 0x02060000
+	/* _PyDict_NewPresized expects a minused parameter, but it actually
+	   creates a dictionary that's the nearest power of two bigger than the
+	   parameter. For example, with the initial minused = 1000, the
+	   dictionary created has size 1024. Of course in a lot of cases that
+	   can be greater than the maximum load factor Python's dict object
+	   expects (= 2/3), so as soon as we cross the threshold we'll resize
+	   anyway. So create a dictionary that's 3/2 the size. Also add some
+	   more to deal with additions outside this function. */
+	file_foldmap = _PyDict_NewPresized((PyDict_Size(dmap) / 5) * 8);
+#else
 	file_foldmap = PyDict_New();
+#endif
+
 	if (file_foldmap == NULL)
 		goto quit;