snmpset on nsExtendCommand

Hello net-snmp-users

I try to modify the nsExtendCommand OID with no success. According to
the documentation of snmpd.conf, this should be possible:
"Both extend and extendfix directives can be configured dynamically,
using SNMP SET requests to the NET-SNMP-EXTEND-MIB."

Do I understand something wrong? What I try is this:

Configfile:
snmpd.conf: extend ls /bin/ls -l

Commandline:
snmpset -v 3 -u USERNAME -A PASSWORD -l authNoPriv
HOSTNAME .1.3.6.1.4.1.8072.1.3.2.2.1.2.2.108.115 s "/bin/echo"

Answer:
Error in packet.
Reason: notWritable (That object does not support modification)
Failed object: NET-SNMP-EXTEND-MIB::nsExtendCommand."ls"

The user has write permissions on the whole oid table. For example the
oid
NET-SNMP-EXTEND-MIB::nsExtendStatus."ls" (.1.3.6.1.4.1.8072.1.3.2.2.1.21.2.108.115) is writable.

The version number of net-snmp is 5.3.

This is a snmpwalk over the nsExtend part:

NET-SNMP-EXTEND-MIB::nsExtendNumEntries.0 = INTEGER: 1
NET-SNMP-EXTEND-MIB::nsExtendCommand."ls" = STRING: /bin/ls
NET-SNMP-EXTEND-MIB::nsExtendArgs."ls" = STRING: -l
NET-SNMP-EXTEND-MIB::nsExtendInput."ls" = STRING:
NET-SNMP-EXTEND-MIB::nsExtendCacheTime."ls" = INTEGER: 5
NET-SNMP-EXTEND-MIB::nsExtendExecType."ls" = INTEGER: exec(1)
NET-SNMP-EXTEND-MIB::nsExtendRunType."ls" = INTEGER: run-on-read(1)
NET-SNMP-EXTEND-MIB::nsExtendStorage."ls" = INTEGER: permanent(4)
NET-SNMP-EXTEND-MIB::nsExtendStatus."ls" = INTEGER: active(1)
NET-SNMP-EXTEND-MIB::nsExtendOutput1Line."ls" = STRING: total 146
NET-SNMP-EXTEND-MIB::nsExtendOutputFull."ls" = STRING: total 146
drwxr-xr-x   2 root root  4096 Jan 18 09:55 bin
drwxr-xr-x   4 root root  1024 Nov 29 14:43 boot
drwxr-xr-x   7 root root  4960 Dec 30 18:26 dev
drwxr-xr-x  52 root root 12288 Jan 18 09:54 etc
drwxr-xr-x   6 root root  4096 Dec  9 13:43 home
drwxr-xr-x   2 root root  4096 Feb 22  2005 initrd
drwxr-xr-x  10 root root  4096 Jan 13 04:02 lib
drwx------   2 root root 16384 Nov 29 15:42 lost+found
drwxr-xr-x   3 root root  4096 Nov 29 14:56 media
drwxr-xr-x   3 root root  4096 Jan 11 10:12 mnt
drwxr-xr-x   2 root root  4096 Dec 28 15:08 opt
dr-xr-xr-x  97 root root     0 Nov 29 15:56 proc
drwxr-x---   4 root root  4096 Jan 18 10:07 root
drwxr-xr-x   2 root root  4096 Nov 29 16:02 sbin
drwxr-xr-x   2 root root  4096 Nov 29 14:42 selinux
drwxr-xr-x   2 root root  4096 Feb 22  2005 srv
drwxr-xr-x   9 root root     0 Nov 29 15:56 sys
drwxrwxrwt  10 root root  4096 Jan 18 09:55 tmp
drwxr-xr-x  14 root root  4096 Nov 29 14:43 usr
drwxr-xr-x  20 root root  4096 Dec  9 13:45 var
NET-SNMP-EXTEND-MIB::nsExtendOutNumLines."ls" = INTEGER: 21
NET-SNMP-EXTEND-MIB::nsExtendResult."ls" = INTEGER: 0
NET-SNMP-EXTEND-MIB::nsExtendOutLine."ls".1 = STRING: total 146
NET-SNMP-EXTEND-MIB::nsExtendOutLine."ls".2 = STRING: drwxr-xr-x   2
root root  4096 Jan 18 09:55 bin
NET-SNMP-EXTEND-MIB::nsExtendOutLine."ls".3 = STRING: drwxr-xr-x   4
root root  1024 Nov 29 14:43 boot
NET-SNMP-EXTEND-MIB::nsExtendOutLine."ls".4 = STRING: drwxr-xr-x   7
root root  4960 Dec 30 18:26 dev
NET-SNMP-EXTEND-MIB::nsExtendOutLine."ls".5 = STRING: drwxr-xr-x  52
root root 12288 Jan 18 09:54 etc
NET-SNMP-EXTEND-MIB::nsExtendOutLine."ls".6 = STRING: drwxr-xr-x   6
root root  4096 Dec  9 13:43 home
NET-SNMP-EXTEND-MIB::nsExtendOutLine."ls".7 = STRING: drwxr-xr-x   2
root root  4096 Feb 22  2005 initrd
NET-SNMP-EXTEND-MIB::nsExtendOutLine."ls".8 = STRING: drwxr-xr-x  10
root root  4096 Jan 13 04:02 lib
NET-SNMP-EXTEND-MIB::nsExtendOutLine."ls".9 = STRING: drwx------   2
root root 16384 Nov 29 15:42 lost+found
NET-SNMP-EXTEND-MIB::nsExtendOutLine."ls".10 = STRING: drwxr-xr-x   3
root root  4096 Nov 29 14:56 media
NET-SNMP-EXTEND-MIB::nsExtendOutLine."ls".11 = STRING: drwxr-xr-x   3
root root  4096 Jan 11 10:12 mnt
NET-SNMP-EXTEND-MIB::nsExtendOutLine."ls".12 = STRING: drwxr-xr-x   2
root root  4096 Dec 28 15:08 opt
NET-SNMP-EXTEND-MIB::nsExtendOutLine."ls".13 = STRING: dr-xr-xr-x  97
root root     0 Nov 29 15:56 proc
NET-SNMP-EXTEND-MIB::nsExtendOutLine."ls".14 = STRING: drwxr-x---   4
root root  4096 Jan 18 10:07 root
NET-SNMP-EXTEND-MIB::nsExtendOutLine."ls".15 = STRING: drwxr-xr-x   2
root root  4096 Nov 29 16:02 sbin
NET-SNMP-EXTEND-MIB::nsExtendOutLine."ls".16 = STRING: drwxr-xr-x   2
root root  4096 Nov 29 14:42 selinux
NET-SNMP-EXTEND-MIB::nsExtendOutLine."ls".17 = STRING: drwxr-xr-x   2
root root  4096 Feb 22  2005 srv
NET-SNMP-EXTEND-MIB::nsExtendOutLine."ls".18 = STRING: drwxr-xr-x   9
root root     0 Nov 29 15:56 sys
NET-SNMP-EXTEND-MIB::nsExtendOutLine."ls".19 = STRING: drwxrwxrwt  10
root root  4096 Jan 18 09:55 tmp
NET-SNMP-EXTEND-MIB::nsExtendOutLine."ls".20 = STRING: drwxr-xr-x  14
root root  4096 Nov 29 14:43 usr
NET-SNMP-EXTEND-MIB::nsExtendOutLine."ls".21 = STRING: drwxr-xr-x  20
root root  4096 Dec  9 13:45 var

Regards
 - Conrad