--- outline.el.orig	2022-02-21 12:08:50.124838087 -0600
+++ outline.el	2022-02-21 13:05:59.087075549 -0600
@@ -294,8 +294,11 @@
 (defvar outline-mode-hook nil
   "This hook is run when outline mode starts.")
 
-(defvar outline-blank-line nil
-  "Non-nil means to leave unhidden blank line before heading.")
+(defcustom outline-blank-line nil
+  "Non-nil means to leave an unhidden blank line before headings."
+  :type 'boolean
+  :version "22.1")
+;;;###autoload(put 'outline-blank-line 'safe-local-variable 'booleanp)
 
 ;;;###autoload
 (define-derived-mode outline-mode text-mode "Outline"