1 files changed, 6 insertions, 2 deletions

diff --git a/lisp/diff.el b/lisp/diff.el
index 891fb970449..ff7906a80c4 100644
--- a/lisp/diff.el
+++ b/lisp/diff.el
@@ -266,8 +266,12 @@ The backup file is the first file given to `diff'."
       (or
        (let ((bak (make-backup-file-name fn)))
          (if (file-exists-p bak) bak))
-       (let* ((dir (file-name-directory fn))
-              (base-versions (concat (file-name-nondirectory fn) ".~"))
+       ;; We use BACKUPNAME to cope with backups stored in a different dir.
+       (let* ((backupname (car (find-backup-file-name fn)))
+              (dir (file-name-directory backupname))
+              (base-versions (concat (file-name-sans-versions
+                                      (file-name-nondirectory backupname))
+                                     ".~"))
               (bv-length (length base-versions)))
          (concat dir
                  (car (sort