diff --git a/core/core-ui.el b/core/core-ui.el
index 9a2b0ee58..5af0bdffd 100644
--- a/core/core-ui.el
+++ b/core/core-ui.el
@@ -469,7 +469,9 @@ derived from `special-mode'."
   (unless (or (bound-and-true-p global-whitespace-mode)
               (bound-and-true-p whitespace-mode)
               (eq major-mode 'fundamental-mode)
-              (derived-mode-p 'special-mode))
+              (eq (get major-mode 'mode-class) 'special)
+              (derived-mode-p 'special-mode)
+              buffer-read-only)
     (require 'whitespace)
     (set (make-local-variable 'whitespace-style)
          (if (bound-and-true-p whitespace-newline-mode)