diff --git a/lisp/autoinsert.el b/lisp/autoinsert.el
index 15fc9ecd469..6b7dcad3899 100644
--- a/lisp/autoinsert.el
+++ b/lisp/autoinsert.el
@@ -171,7 +171,7 @@ If this contains a %s, that will be replaced by the matching rule."
      ";;; Directory Local Variables         -*- no-byte-compile: t; -*-\n"
      ";;; For more information see (info \"(emacs) Directory Variables\")\n\n"
      "(("
-     '(setq v1 (let (modes)
+     '(setq v1 (let ((modes '("nil")))
                  (mapatoms (lambda (mode)
                              (let ((name (symbol-name mode)))
                                (when (string-match "-mode\\'" name)