Chown: invalid group after setting daemonGroup

[ericsmitt]

Expected behaviour

It doesn't add group 'defender' in postinst after this setting:
daemonGroup in Linux := "adm"

Project settings

daemonGroup := "adm", // group with read rights /var/log/auth.log
daemonUser in Linux := "defender",
daemonGroup in Linux := "adm", // group with read rights /var/log/auth.log

Actual behaviour during installation

Selecting previously unselected package defender.
(Reading database ... 252290 files and directories currently installed.)
Preparing to unpack .../defender_0.1.1-SNAPSHOT_all.deb ...
Unpacking defender (0.1.1-SNAPSHOT) ...
Setting up defender (0.1.1-SNAPSHOT) ...
Creating system user: defender in adm with defender daemon-user and shell /bin/false
chown: invalid group: ‘defender:defender’
dpkg: error processing package defender (--install):
subprocess installed post-installation script returned error exit status 1
Processing triggers for ureadahead (0.100.0-19) ...
Errors were encountered while processing:
defender

Postinst script

addGroup adm ""
addUser defender "" adm "defender daemon-user" "/bin/false"

chown defender:defender /var/lib/defender/persistence/journal
chown defender:defender /var/lib/defender/persistence/snapshots
chown defender:adm /var/log/defender