1 files changed, 4 insertions, 0 deletions

diff --git a/lisp/cus-edit.el b/lisp/cus-edit.el
index e700cd47d16..53f92f2243b 100644
--- a/lisp/cus-edit.el
+++ b/lisp/cus-edit.el
@@ -1055,6 +1055,8 @@ then prompt for the MODE to customize."
 (defun customize-option (symbol)
   "Customize SYMBOL, which must be a user option variable."
   (interactive (custom-variable-prompt))
+  (unless symbol
+    (error "No variable specified"))
   (let ((basevar (indirect-variable symbol)))
     (custom-buffer-create (list (list basevar 'custom-variable))
                           (format "*Customize Option: %s*"
@@ -1070,6 +1072,8 @@ then prompt for the MODE to customize."
   "Customize SYMBOL, which must be a user option variable.
 Show the buffer in another window, but don't select it."
   (interactive (custom-variable-prompt))
+  (unless symbol
+    (error "No variable specified"))
   (let ((basevar (indirect-variable symbol)))
     (custom-buffer-create-other-window
      (list (list basevar 'custom-variable))