Index: usr.sbin/jail/jail.c
===================================================================
--- usr.sbin/jail/jail.c	(revision 195903)
+++ usr.sbin/jail/jail.c	(working copy)
@@ -82,6 +82,7 @@
 	{ "security.jail.socket_unixiproute_only",
 	  "allow.socket_af", "allow.nosocket_af" },
 };
+static char disable[] = "disable";
 
 extern char **environ;
 
@@ -257,6 +258,17 @@
 				set_param("enforce_statfs", enforce_statfs);
 			}
 		}
+
+		/*
+		 * In the legacy jail world the defaults have been
+		 * 'disable' rather than 'inherit'.
+		 */
+		if (ip4_addr == NULL)
+			set_param("ip4", disable);
+#ifdef INET6
+		if (ip6_addr == NULL)
+			set_param("ip6", disable);
+#endif
 	}
 	if (ip4_addr != NULL)
 		set_param("ip4.addr", ip4_addr);