(font-lock-ensure-function): Fix bug#22399

* lisp/font-lock.el (font-lock-ensure-function): Fix handling when
font-lock-mode is not enabled (bug#22399).

1 files changed, 7 insertions, 1 deletions

diff --git a/lisp/font-lock.el b/lisp/font-lock.el
index 3c1f01d5886..6f94f353c90 100644
--- a/lisp/font-lock.el
+++ b/lisp/font-lock.el
@@ -1074,7 +1074,13 @@ accessible portion of the current buffer."
 
 (defvar font-lock-ensure-function
   (lambda (_beg _end)
-    (unless font-lock-fontified (font-lock-default-fontify-buffer)))
+    (unless font-lock-fontified
+      (font-lock-default-fontify-buffer)
+      (unless font-lock-mode
+        ;; If font-lock is not enabled, we don't have the hooks in place to
+        ;; track modifications, so a subsequent call to font-lock-ensure can't
+        ;; assume that the fontification is still valid.
+        (setq font-lock-fontified nil))))
   "Function to make sure a region has been fontified.
 Called with two arguments BEG and END.")