diff --git a/n2vc/vnf.py b/n2vc/vnf.py
index 0d9530e..11ce3c8 100644
--- a/n2vc/vnf.py
+++ b/n2vc/vnf.py
@@ -457,8 +457,8 @@
             if all(k in machine_spec for k in ['host', 'user']):
                 # Enlist an existing machine as a Juju unit
                 machine = await model.add_machine(spec='ssh:{}@{}:{}'.format(
-                    machine_spec['user'],
-                    machine_spec['host'],
+                    machine_spec['username'],
+                    machine_spec['hostname'],
                     self.GetPrivateKeyPath(),
                 ))
                 to = machine.id
diff --git a/tests/base.py b/tests/base.py
index 912eab9..663e89a 100644
--- a/tests/base.py
+++ b/tests/base.py
@@ -740,8 +740,8 @@
             )
 
             machine_spec = {
-                'host': hostname,
-                'user': 'ubuntu',
+                'hostname': hostname,
+                'username': 'ubuntu',
             }
 
         await self.n2vc.DeployCharms(