Please extract the attached gzipped tarball into ~. Inside ~, start Emacs with an init file containing the following: --8<---------------cut here---------------start------------->8--- (custom-set-variables  ;; custom-set-variables was added by Custom.  ;; If you edit it by hand, you could mess it up, so be careful.  ;; Your init file should contain only one such instance.  ;; If there is more than one, they won't work right.  '(backup-directory-alist (quote (("." . ".~")))) ) (custom-set-faces  ;; custom-set-faces was added by Custom.  ;; If you edit it by hand, you could mess it up, so be careful.  ;; Your init file should contain only one such instance.  ;; If there is more than one, they won't work right.  ) --8<---------------cut here---------------end--------------->8--- Perform the following steps: 1. C-x d ~/dired-diff-bug-1 2. j dummy 3. =  I expected (according to the documentation of dired-diff) to see the diff of dummy with its backup.  Instead a diff error occurs.  I have saved the diff error buffer to diff-error-dummy.txt and attached it. Now perform the following steps: 1. C-x d ~/dired-diff-bug-1/.~ 2. j dummy~ 3. = . A similar diff error occurs. It is also unexpected.  I have saved the diff error buffer in diff-error-dummy~.txt and attached it. I have also attached a dribble file. report-emacs-bug was invoked from another Emacs session, also invoked with an init file having the contents specified above. In GNU Emacs 25.1.1 (x86_64-unknown-linux-gnu, GTK+ Version 3.18.9)  of 2016-07-25 built on jorge-HP-G42 Windowing system distributor 'The X.Org Foundation', version 11.0.11803000 System Description: Ubuntu 16.04.1 LTS Configured using:  'configure --prefix=/usr/local/emacs/ --with-modules' Configured features: XPM JPEG TIFF GIF PNG RSVG IMAGEMAGICK SOUND GPM DBUS GCONF GSETTINGS NOTIFY ACL LIBSELINUX GNUTLS LIBXML2 FREETYPE M17N_FLT LIBOTF XFT ZLIB TOOLKIT_SCROLL_BARS GTK3 X11 MODULES Important settings:   value of $LC_MONETARY: en_DK.UTF-8   value of $LC_NUMERIC: en_DK.UTF-8   value of $LC_TIME: en_DK.UTF-8   value of $LANG: en_US.UTF-8   value of $XMODIFIERS: @im=ibus   locale-coding-system: utf-8-unix Major mode: Fundamental Minor modes in effect:   tooltip-mode: t   global-eldoc-mode: t   electric-indent-mode: t   mouse-wheel-mode: t   tool-bar-mode: t   menu-bar-mode: t   file-name-shadow-mode: t   global-font-lock-mode: t   blink-cursor-mode: t   auto-composition-mode: t   auto-encryption-mode: t   auto-compression-mode: t   buffer-read-only: t   line-number-mode: t   transient-mark-mode: t Recent messages: For information about GNU Emacs and the GNU system, type C-h C-a. 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code-pages mule custom widget hashtable-print-readable backquote dbusbind inotify dynamic-setting system-font-setting font-render-setting move-toolbar gtk x-toolkit x multi-tty make-network-process emacs) Memory information: ((conses 16 110174 5697)  (symbols 48 22087 0)  (miscs 40 485 158)  (strings 32 22517 5631)  (string-bytes 1 745738)  (vectors 16 15009)  (vector-slots 8 473639 3924)  (floats 8 196 3)  (intervals 56 247 1)  (buffers 976 20)  (heap 1024 44160 1133)) -- • I am Brazilian.  I hope my English is correct and I welcome corrections. • Please adopt free formats like PDF, ODF, LaTeX, Opus, WebM and 7z. • Free software for Android: https://f-droid.org/