Without bind-address, the server listen in IPv6 only

WHen I start a server without bind-address option, or with "bind-address = ::", the server only listens on IPv6.

The mysql doc indicates it should listen on both IPv6 and IPv4.

root@bjo-test-sql-001:~# lsof -i TCP | grep mysql
mysqld 32594 mysql 11u IPv4 99449675 0t0 TCP *:4567 (LISTEN)
mysqld 32594 mysql 13u IPv4 99449678 0t0 TCP test-sql-001.lan.xxx.com:53605->192.168.2.182:4567 (ESTABLISHED)
mysqld 32594 mysql 14u IPv4 99449680 0t0 TCP test-sql-001.lan.xxx.com:33919->192.168.2.183:4567 (ESTABLISHED)
mysqld 32594 mysql 21u IPv6 99450186 0t0 TCP *:mysql (LISTEN)

root@bjo-test-sql-001:~# dpkg -s percona-xtradb-cluster-full-56

Package: percona-xtradb-cluster-full-56
Status: install ok installed
Priority: extra
Section: database
Installed-Size: 57
Maintainer: Percona Server Development Team <email address hidden>
Architecture: amd64
Source: percona-xtradb-cluster-5.6
Version: 5.6.26-25.12-1.trusty
Depends: percona-xtradb-cluster-server-5.6 (>= 5.6.26-25.12-1.trusty), percona-xtradb-cluster-client-5.6 (>= 5.6.26-25.12-1.trusty), percona-xtradb-cluster-galera-3, percona-xtradb-cluster-test-5.6 (>= 5.6.26-25.12-1.trusty), percona
-xtradb-cluster-5.6-dbg (>= 5.6.26-25.12-1.trusty), percona-xtradb-cluster-garbd-3, percona-xtradb-cluster-galera3-dbg, percona-xtradb-cluster-server-debug-5.6
Description: Percona XtraDB Cluster with Galera
 This is a meta-package providing PXC56 server, client, galera-3, test and debug packages.
Homepage: http://www.percona.com/software/percona-xtradb-cluster/