--- tcpdump-3.9.1/print-isoclns.c.orig	2005-07-06 15:05:30.000000000 +0200
+++ tcpdump-3.9.1/print-isoclns.c	2005-07-06 15:05:34.000000000 +0200
@@ -2121,13 +2121,15 @@ static int isis_print (const u_int8_t *p
             }
             tmp --;
             printf("\n\t      LAN address length %u bytes ",lan_alen);
-	    while (tmp >= lan_alen) {
-                if (!TTEST2(*tptr, lan_alen))
-                    goto trunctlv;
-                printf("\n\t\tIS Neighbor: %s",isis_print_id(tptr,lan_alen));
-                tmp -= lan_alen;
-                tptr +=lan_alen;
-            }
+	    if(lan_alen >= SYSTEM_ID_LEN) {
+		while (tmp >= lan_alen) {
+		    if (!TTEST2(*tptr, lan_alen))
+			goto trunctlv;
+		    printf("\n\t\tIS Neighbor: %s",isis_print_id(tptr,lan_alen));
+		    tmp -= lan_alen;
+		    tptr +=lan_alen;
+		}
+	    }
             break;
 
 	case ISIS_TLV_PADDING: