diff --git a/lisp/t-mouse.el b/lisp/t-mouse.el
index fc174176cd6..a1af53d8c46 100644
--- a/lisp/t-mouse.el
+++ b/lisp/t-mouse.el
@@ -1,4 +1,4 @@
-;;; t-mouse.el --- mouse support within the text terminal
+;;; t-mouse.el --- mouse support within the text terminal  -*- lexical-binding:t -*-
 
 ;; Author: Nick Roberts <nickrob@gnu.org>
 ;; Maintainer: emacs-devel@gnu.org