diff --git a/test/crossmod_opaque.py b/test/crossmod_opaque.py
index f649921c..06637385 100644
--- a/test/crossmod_opaque.py
+++ b/test/crossmod_opaque.py
@@ -1,3 +1,4 @@
+# -*- coding: iso-latin-1 -*-
 # Copyright Gottfried Ganßauge 2006.
 # Distributed under the Boost Software License, Version 1.0. (See
 # accompanying file LICENSE_1_0.txt or copy at