[SNMP4J] TestSubagent not walkable

[Ryan]

Using NET-SNMP version 5.4.1, running the TestSubagent class does not give
me results when using snmpwalk with the OID .1.3.6.1.4.1.4976.10.1.1.100.4.1

The agentx subagent registers correctly, as confirmed by a protocol trace
showing the agentx open pdu, agent caps pdu, and all register pdus, but
using snmpwalk to traverse the registered OID returns nothing:

($:~) snmpwalk -v 2c -c public localhost .1.3.6.1.4.1.4976
SNMPv2-SMI::enterprises.4976 = No more variables left in this MIB View (It
is past the end of the MIB tree)

Is there something obvious I'm missing?

Thank you,
Ryan