diff --git a/src/netif/ppp/chpms.c b/src/netif/ppp/chpms.c
index 0c7521f2..582cfd2d 100644
--- a/src/netif/ppp/chpms.c
+++ b/src/netif/ppp/chpms.c
@@ -1,4 +1,7 @@
 /*** WARNING - THIS CODE HAS NOT BEEN FINISHED! ***/
+/*** The original PPPD code is written in a way to require either the UNIX DES
+     encryption functions encrypt(3) and setkey(3) or the DES library libdes.
+     Since both is not included in lwIP, MSCHAP currently does not work! */
 /*****************************************************************************
 * chpms.c - Network MicroSoft Challenge Handshake Authentication Protocol program file.
 *