diff --git a/src/config.h b/src/config.h
index f3a9fe7..7187ffa 100644
--- a/src/config.h
+++ b/src/config.h
@@ -43,7 +43,8 @@
 #define DNSSEC_MIN_TTL 60 /* DNSKEY and DS records in cache last at least this long */
 #define HOSTSFILE "/etc/hosts"
 #define ETHERSFILE "/etc/ethers"
-#define DEFLEASE 3600 /* default lease time, 1 hour */
+#define DEFLEASE 3600 /* default DHCPv4 lease time, one hour */
+#define DEFLEASE6 (3600*24) /* default lease time for DHCPv6. One day. */
 #define CHUSER "nobody"
 #define CHGRP "dip"
 #define TFTP_MAX_CONNECTIONS 50 /* max simultaneous connections */