diff --git a/src/charm.py b/src/charm.py
index d7b961b..84a4fa9 100755
--- a/src/charm.py
+++ b/src/charm.py
@@ -147,9 +147,7 @@ class CephISCSIGatewayCharmBase(
     DEFAULT_TARGET = "iqn.2003-01.com.ubuntu.iscsi-gw:iscsi-igw"
     REQUIRED_RELATIONS = ['ceph-client', 'cluster']
 
-    # Two has been tested but four is probably fine too but needs
-    # validating
-    ALLOWED_UNIT_COUNTS = [2]
+    ALLOWED_UNIT_COUNTS = [2, 4]
 
     CEPH_CONFIG_PATH = Path('/etc/ceph')
     CEPH_ISCSI_CONFIG_PATH = CEPH_CONFIG_PATH / 'iscsi'
diff --git a/tests/bundles/focal.yaml b/tests/bundles/focal.yaml
index a980504..2ee6e3c 100644
--- a/tests/bundles/focal.yaml
+++ b/tests/bundles/focal.yaml
@@ -20,6 +20,8 @@ machines:
   '13':
   '14':
   '15':
+  '16':
+  '17':
 applications:
   ubuntu:
     charm: cs:ubuntu
@@ -30,12 +32,14 @@ applications:
       - '15'
   ceph-iscsi:
     charm: ../../ceph-iscsi.charm
-    num_units: 2
+    num_units: 4
     options:
       gateway-metadata-pool: iscsi-foo-metadata
     to:
       - '0'
       - '1'
+      - '16'
+      - '17'
   ceph-osd:
     charm: cs:~openstack-charmers-next/ceph-osd
     num_units: 6