--- rxvt-unicode/ptytty.m4	2006/01/22 00:48:13	1.1
+++ rxvt-unicode/ptytty.m4	2006/01/22 01:00:46	1.2
@@ -1,3 +1,6 @@
+dnl this file is part of libptytty, do not make local modifications
+dnl http://software.schmorp.de/pkg/libptytty
+
 AC_DEFUN([PTY_CHECK],
 [
 AC_CHECK_HEADERS( \