diff --git a/doc/examples/plot_radon_transform.py b/doc/examples/plot_radon_transform.py
index d457d5a6..61175f8a 100644
--- a/doc/examples/plot_radon_transform.py
+++ b/doc/examples/plot_radon_transform.py
@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 """
 ===============
 Radon transform