diff --git a/charms_openstack/plugins/classes.py b/charms_openstack/plugins/classes.py
index 39b2554..64e813d 100644
--- a/charms_openstack/plugins/classes.py
+++ b/charms_openstack/plugins/classes.py
@@ -121,12 +121,11 @@ class BaseOpenStackCephCharm(object):
         return os.path.join(self.snap_path_prefix,
                             self.ceph_keyring_path_prefix)
 
-    def configure_ceph_keyring(self, interface,
-                               cluster_name=None):
+    def configure_ceph_keyring(self, key, cluster_name=None):
         """Creates or updates a Ceph keyring file.
 
-        :param interface: Interface with ``key`` property.
-        :type interface: Any class that has a property named ``key``.
+        :param key: Key data
+        :type key: str
         :param cluster_name: (Optional) Name of Ceph cluster to operate on.
                              Defaults to value of ``self.ceph_cluster_name``.
         :type cluster_name: str
@@ -145,7 +144,7 @@ class BaseOpenStackCephCharm(object):
         cmd = [
             'ceph-authtool', keyring_absolute_path,
             '--create-keyring', '--name={}'.format(self.ceph_key_name),
-            '--add-key', interface.key, '--mode', '0600',
+            '--add-key', key, '--mode', '0600',
         ]
         try:
             subprocess.check_call(cmd)
@@ -231,10 +230,10 @@ class CephCharm(charms_openstack.charm.OpenStackCharm,
                             self.ceph_keyring_path_prefix,
                             self.ceph_service_name)
 
-    def configure_ceph_keyring(self, interface, cluster_name=None):
+    def configure_ceph_keyring(self, key, cluster_name=None):
         """Override parent function to add symlink in ``/etc/ceph``."""
         keyring_absolute_path = super().configure_ceph_keyring(
-            interface, cluster_name=cluster_name)
+            key, cluster_name=cluster_name)
         symlink_absolute_path = os.path.join(
             '/etc/ceph',
             os.path.basename(keyring_absolute_path))
diff --git a/unit_tests/charms_openstack/plugins/test_classes.py b/unit_tests/charms_openstack/plugins/test_classes.py
index c08491c..5476713 100644
--- a/unit_tests/charms_openstack/plugins/test_classes.py
+++ b/unit_tests/charms_openstack/plugins/test_classes.py
@@ -70,9 +70,8 @@ class TestOpenStackCephConsumingCharm(BaseOpenStackCharmTest):
                           return_value='sarepta')
         self.patch_object(cpl.subprocess, 'check_call')
         self.patch_object(cpl.shutil, 'chown')
-        interface = mock.MagicMock()
-        interface.key = 'KEY'
-        self.assertEqual(self.target.configure_ceph_keyring(interface),
+        key = 'KEY'
+        self.assertEqual(self.target.configure_ceph_keyring(key),
                          '/etc/ceph/ceph.client.sarepta.keyring')
         self.isdir.assert_called_with('/etc/ceph')
         self.mkdir.assert_called_with('/etc/ceph',
@@ -85,7 +84,7 @@ class TestOpenStackCephConsumingCharm(BaseOpenStackCharmTest):
         ])
         self.target.user = 'ceph'
         self.target.group = 'ceph'
-        self.target.configure_ceph_keyring(interface)
+        self.target.configure_ceph_keyring(key)
         self.chown.assert_called_with(
             '/etc/ceph/ceph.client.sarepta.keyring',
             user='ceph', group='ceph')
@@ -94,11 +93,11 @@ class TestOpenStackCephConsumingCharm(BaseOpenStackCharmTest):
         self.check_call.side_effect = [
             subprocess.CalledProcessError(42, [], ''), None]
         with self.assertRaises(subprocess.CalledProcessError):
-            self.target.configure_ceph_keyring(interface)
+            self.target.configure_ceph_keyring(key)
         self.check_call.reset_mock()
         self.check_call.side_effect = [
             subprocess.CalledProcessError(1, [], ''), None]
-        self.target.configure_ceph_keyring(interface)
+        self.target.configure_ceph_keyring(key)
         self.check_call.assert_has_calls([
             mock.call([
                 'ceph-authtool',
@@ -140,13 +139,12 @@ class TestCephCharm(BaseOpenStackCharmTest):
         self.patch_object(cpl.subprocess, 'check_call')
         self.patch_object(cpl.shutil, 'chown')
         self.patch_object(cpl.os, 'symlink')
-        interface = mock.MagicMock()
-        interface.key = 'KEY'
+        key = 'KEY'
         self.patch_object(cpl.os.path, 'exists', return_value=True)
         self.patch_object(cpl.os, 'readlink')
         self.patch_object(cpl.os, 'remove')
         self.readlink.side_effect = OSError
-        self.target.configure_ceph_keyring(interface)
+        self.target.configure_ceph_keyring(key)
         self.isdir.assert_called_with('/var/lib/ceph/sarepta')
         self.mkdir.assert_called_with('/var/lib/ceph/sarepta',
                                       owner='root', group='root', perms=0o750)
@@ -166,7 +164,7 @@ class TestCephCharm(BaseOpenStackCharmTest):
             '/etc/ceph/ceph.client.sarepta.keyring')
         self.readlink.side_effect = None
         self.readlink.return_value = '/some/where/else'
-        self.target.configure_ceph_keyring(interface)
+        self.target.configure_ceph_keyring(key)
         self.remove.assert_called_with('/etc/ceph/ceph.client.sarepta.keyring')
 
     def test_install(self):