diff --git a/extras/interval_map.py b/extras/interval_map.py
index 2a0c05679..7e6c5cdb5 100644
--- a/extras/interval_map.py
+++ b/extras/interval_map.py
@@ -1,3 +1,5 @@
+# -*- coding: utf-8 -*-
+
 from bisect import bisect_left, bisect_right
 from itertools import izip