(find-backup-file-name) [ms-dos]: If support for long

file names is not available, behave as if version-control were set
to never.

1 files changed, 5 insertions, 1 deletions

diff --git a/lisp/files.el b/lisp/files.el
index 6fc452545e5..904d04636f5 100644
--- a/lisp/files.el
+++ b/lisp/files.el
@@ -2386,7 +2386,11 @@ Uses `backup-directory-alist' in the same way as does
     ;; Run a handler for this function so that ange-ftp can refuse to do it.
     (if handler
         (funcall handler 'find-backup-file-name fn)
-      (if (eq version-control 'never)
+      (if (or (eq version-control 'never)
+              ;; We don't support numbered backups on plain MS-DOS
+              ;; when long file names are unavailable.
+              (and (eq system-type 'ms-dos)
+                   (not (msdos-long-file-names))))
           (list (make-backup-file-name fn))
         (let* ((basic-name (make-backup-file-name-1 fn))
                (base-versions (concat (file-name-nondirectory basic-name)