agent[x]PingInterval

I am using net-snmp-5.2.2
My snmpd.conf looks like:

rocommunity  public
master agentx
agentxPingInterval 10

smuxpeer 1.3.6.1.4.1.2.3.1.2.1.2.         gated_password
smuxpeer 1.3.6.1.4.1.2.3.1.2.2.1.1.2.     dpid_password

smuxpeer 1.3.6.1.4.1.2.3.1.2.3.1.1.       muxatmd_password
smuxpeer 1.3.6.1.4.1.2.3.1.2.1.5.         clsmuxpd_password

When I look in my snmpd.log, I found this:

NET-SNMP version 5.2.2 restarted
Turning on AgentX master support.
.../share/snmp/snmpd.conf: line 21: Warning: Unknown token:
agentxPingInterval.

I try to put agentPingInterval instead in my snmpd.conf but got the same
warning (but with Unknown token: agentPingInterval this time).
Is this directive supported with net-snmp-5.2.2 ?? 
Where is my mistake??
Thanks in advance.