diff --git a/lisp/cdl.el b/lisp/cdl.el
index adc05f1bb52..c8025a9f530 100644
--- a/lisp/cdl.el
+++ b/lisp/cdl.el
@@ -1,4 +1,4 @@
-;;; cdl.el --- Common Data Language (CDL) utility functions for GNU Emacs
+;;; cdl.el --- Common Data Language (CDL) utility functions for GNU Emacs -*- lexical-binding: t -*-
 
 ;; Copyright (C) 1993, 2001-2020 Free Software Foundation, Inc.