2 files changed, 5 insertions, 1 deletions

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index 2321854e545..ede723e6d6b 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,5 +1,8 @@
 2013-11-23  Ivan Shmakov  <ivan@siamics.net>  (tiny change)
 
+        * vc/diff-mode.el (diff-mode): Only allow diff-default-read-only
+        to set buffer-read-only to t, never to nil.  (Bug#15938)
+
         * textmodes/tex-mode.el (latex-noindent-environments):
         Add safe-local-variable property.  (Bug#15936)
 
diff --git a/lisp/vc/diff-mode.el b/lisp/vc/diff-mode.el
index e945d6ef160..0bf0b05c7d5 100644
--- a/lisp/vc/diff-mode.el
+++ b/lisp/vc/diff-mode.el
@@ -1366,7 +1366,8 @@ a diff with \\[diff-reverse-direction].
 
   (diff-setup-whitespace)
 
-  (setq buffer-read-only diff-default-read-only)
+  (if diff-default-read-only
+      (setq buffer-read-only t))
   ;; setup change hooks
   (if (not diff-update-on-the-fly)
       (add-hook 'write-contents-functions 'diff-write-contents-hooks nil t)