--- lisp/diff-mode.el	2007-08-17 06:03:27.000000000 +0200
+++ lisp/diff-mode.el	2007-08-18 00:48:25.000000000 +0200
@@ -667,6 +667,7 @@
       (or (ignore-errors (diff-beginning-of-file))
 	  (re-search-forward diff-file-header-re nil t)))
     (let ((fs (diff-hunk-file-names old)))
+      (setq fs (delete "/dev/null" fs))
       (if prefix (setq fs (mapcar (lambda (f) (concat prefix f)) fs)))
       (or
        ;; use any previously used preference