diff --git a/lisp/loadup.el b/lisp/loadup.el
index e449b2b5d30..1bfcad604bf 100644
--- a/lisp/loadup.el
+++ b/lisp/loadup.el
@@ -225,8 +225,9 @@
       (setq tem (cdr tem))))
   (princ ")))\n" (current-buffer))
   (write-region (point-min) (point-max)
-		(expand-file-name (format "../lisp/fns-%s.el" emacs-version)
-				  invocation-directory))
+		(expand-file-name (convert-standard-filename
+				   (format "../lisp/fns-%s.el" emacs-version))
+				   invocation-directory))
   (erase-buffer))
 (setq load-history nil)
 (set-buffer-modified-p nil)