diff --git a/ppp.c b/ppp.c
index ac244a9..f34a646 100644
--- a/ppp.c
+++ b/ppp.c
@@ -899,7 +899,7 @@ void processlcp(sessionidt s, tunnelidt t, uint8_t *p, uint16_t l)
 							LOG(3, s, t, "    Remote requested PAP authentication...%sing\n",
 								authtype ? "accept" : "reject");
 						}
-						else if (proto == PPPCHAP && length > 4 && *(o + 4) == 5)
+						else if (proto == PPPCHAP && (length == 4 || (length > 4 && *(o + 4) == 5)))
 						{
 							authtype = config->radius_authtypes & AUTHCHAP;
 							LOG(3, s, t, "    Remote requested CHAP authentication...%sing\n",