1 files changed, 4 insertions, 0 deletions

diff --git a/lisp/font-lock.el b/lisp/font-lock.el
index 5c23041c3a6..a737e0452f2 100644
--- a/lisp/font-lock.el
+++ b/lisp/font-lock.el
@@ -335,6 +335,8 @@ the face is also set; its value is the face name."
       (beginning-of-line)
       (if loudly (message "Fontifying %s... (syntactically...)" (buffer-name)))
       (let ((buffer-read-only nil)
+            ;; Suppress all undo activity.
+            (buffer-undo-list t)
             (modified (buffer-modified-p))
             (cstart (if comment-start-skip
                         (concat "\\s\"\\|" comment-start-skip)
@@ -449,6 +451,7 @@ the face is also set; its value is the face name."
 
 (defun font-lock-unfontify-region (beg end)
   (let ((modified (buffer-modified-p))
+        (buffer-undo-list t)
         (buffer-read-only nil))
     (remove-text-properties beg end '(face nil))
     (set-buffer-modified-p modified)))
@@ -491,6 +494,7 @@ the face is also set; its value is the face name."
         (keywords font-lock-keywords)
         (count 0)
         (buffer-read-only nil)
+        (buffer-undo-list t)
         (modified (buffer-modified-p))
         (old-syntax (syntax-table))
         (bufname (buffer-name)))