can't update object: permission denied

Trying to delete a lease from the DHCP server with the following procedure and ending up with the following message.

can't update object: permission denied

# omshell 
> connect
obj: <null>
> new lease
obj: lease
> set ip-address = 192.168.6.20
obj: lease
ip-address = c0:a8:06:14
> open
obj: lease
ip-address = c0:a8:06:14
state = 00:00:00:02
client-hostname = "rhel7-c1"
subnet = 00:00:00:02
pool = 00:00:00:03
hardware-address = 08:00:27:a5:22:0a
hardware-type = 00:00:00:01
ends = 5f:4d:8a:81
starts = 5f:4d:1a:01
tstp = 00:00:00:00
tsfp = 00:00:00:00
atsfp = 00:00:00:00
cltt = 5f:4d:1a:01
flags = 00

> unset ip-address       
obj: lease
ip-address = <null>
state = 00:00:00:02
client-hostname = "rhel7-c1"
subnet = 00:00:00:02
pool = 00:00:00:03
hardware-address = 08:00:27:a5:22:0a
hardware-type = 00:00:00:01
ends = 5f:4d:8a:81
starts = 5f:4d:1a:01
tstp = 00:00:00:00
tsfp = 00:00:00:00
atsfp = 00:00:00:00
cltt = 5f:4d:1a:01
flags = 00

> update
can't update object: permission denied
obj: lease
ip-address = <null>
state = 00:00:00:02
client-hostname = "rhel7-c1"
subnet = 00:00:00:02
pool = 00:00:00:03
hardware-address = 08:00:27:a5:22:0a
hardware-type = 00:00:00:01
ends = 5f:4d:8a:81
starts = 5f:4d:1a:01
tstp = 00:00:00:00
tsfp = 00:00:00:00
atsfp = 00:00:00:00
cltt = 5f:4d:1a:01
flags = 00

# dhcpd --version
isc-dhcpd-4.2.5