See the attachment.
Paolo
--- orig/sed/regexp.c +++ mod/sed/regexp.c @@ -113,7 +113,7 @@ compile_regex_1 (new_regex, needed_sub) { char buf[200]; sprintf(buf, _("invalid reference \\%d on `s' command's RHS"), - needed_sub); + needed_sub - 1); bad_prog(buf); } }