unable to add a 1.7.2 node to a 1.8.0 cluster

Failed to add node 10.1.5.58:8091 to cluster. Join completion call failed. Failed to start ns_server cluster processes back. Logs might have more details. (repeated 1 times)

error :

Conflicting configuration changes to field

{node,'ns_1@10.1.5.58',ns_log}

:
[{'_vclock',[{'ns_1@10.1.5.58',{1,63490331315}},
{'ns_1@127.0.0.1',{1,63490331310}}]},

{filename,"/opt/membase/var/lib/membase/data/ns_log"}

] and
[{'_vclock',[{'ns_1@10.1.5.58',{1,63490331239}},
{'ns_1@127.0.0.1',{1,63489992446}}]},

{filename,"/opt/couchbase/var/lib/couchbase/data/ns_log"}

], choosing the former, which looks newer.