diff --git a/purescript-indentation.el b/purescript-indentation.el
index 781ae94..1312553 100644
--- a/purescript-indentation.el
+++ b/purescript-indentation.el
@@ -1,4 +1,4 @@
-;;; purescript-indentation.el -- indentation module for PureScript Mode
+;;; purescript-indentation.el -- indentation module for PureScript Mode -*- lexical-binding: t -*-
 
 ;; Copyright (C) 2009  Kristof Bastiaensen