Failed object: NET-SNMP-EXTEND-MIB::nsExtendStatus."command9"

[GenoWang]

Hi, I try to add a shell command into config file with

snmpset -m +NET-SNMP-EXTEND-MIB -v 2c -c private localhost 'nsExtendStatus."command9"' = createAndGo 'nsExtendCommand."command9"' = /bin/echo 'nsExtendArgs."command9"' = 'hello rio is here'

but failed with

Error in packet.
Reason: (genError) A general failure occured
Failed object: NET-SNMP-EXTEND-MIB::nsExtendStatus."command9"

why is that happen? NET-SNMP version is 5.7.3.