diff --git a/lisp/vc/ediff-util.el b/lisp/vc/ediff-util.el
index b2b92b17e28..0cbea2c28d7 100644
--- a/lisp/vc/ediff-util.el
+++ b/lisp/vc/ediff-util.el
@@ -563,8 +563,9 @@ to invocation.")
 	    (set-visited-file-name merge-buffer-file))))
     (ediff-with-current-buffer ediff-buffer-C
       (setq buffer-offer-save t) ; ask before killing buffer
-      ;; make sure the contents is auto-saved
-      (auto-save-mode 1))
+      (when make-backup-files
+        ;; make sure the contents is auto-saved
+        (auto-save-mode 1)))
     ))