diff --git a/lisp/ruler-mode.el b/lisp/ruler-mode.el
index 840934f1693..be30afd7861 100644
--- a/lisp/ruler-mode.el
+++ b/lisp/ruler-mode.el
@@ -123,8 +123,7 @@ or remove a tab stop.  \\[ruler-mode-toggle-show-tab-stops] or
   "Ensure WIDGET value is a valid character value."
   (save-excursion
     (let ((value (widget-value widget)))
-      (if (char-valid-p value)
-          nil
+      (unless (characterp value)
         (widget-put widget :error
                     (format "Invalid character value: %S" value))
         widget))))