unpack_sequence(): In finally clause, watch out for Py_DECREF
evaluating its arguments twice.
diff --git a/Python/ceval.c b/Python/ceval.c
index e08e1c9..c920d30 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -2076,8 +2076,8 @@
 				"unpack sequence of wrong size");
 	/* fall through */
 finally:
-	for (; i > 0; i--)
-		Py_DECREF(*sp++);
+	for (; i > 0; i--, sp++)
+		Py_DECREF(*sp);
 
 	return 0;
 }