Why Ceph monitor daemons are giving this error "[ERR] : mon_lease_ack_timeout (20) must be greater than mon_lease (20)" and failing to start ?

Issue

• Why Ceph monitor daemons are giving this error "[ERR] : mon_lease_ack_timeout (20) must be greater than mon_lease (20)" and failing to start ?
• Logs in /var/log/messages file:

mon-node1 systemd: Started /usr/local/bin/bash -c ulimit -n 131072; /usr/bin/ceph-mon -i mon-node1 --pid-file /var/run/ceph/mon.mon-node1.pid -c /etc/ceph/ceph.conf --cluster ceph -f.
mon-node1 systemd: Starting /usr/local/bin/bash -c ulimit -n 131072; /usr/bin/ceph-mon -i mon-node1 --pid-file /var/run/ceph/mon.mon-node1.pid -c /etc/ceph/ceph.conf --cluster ceph -f...
mon-node1 bash: starting mon.mon-node1 rank 1 at 10.115.96.12:6789/0 mon_data /var/lib/ceph/mon/ceph-mon-node1 fsid 54a41087-9519-43b8-ac0f-c9cdaa7a5273
mon-node1 bash: 2016-01-10 02:37:20.372412 7fc63dfb07c0 -1 log_channel(cluster) log [ERR] : mon_lease_ack_timeout (20) must be greater than mon_lease (20)
mon-node1 bash: 2016-01-10 02:37:20.372464 7fc63dfb07c0 -1 mon.mon-node1@-1(probing) e34 option sanitization failed!
mon-node1 bash: 2016-01-10 02:37:20.372468 7fc63dfb07c0 -1 failed to initialize