diff --git a/charms_openstack/charm/core.py b/charms_openstack/charm/core.py
index c12b911..74237e4 100644
--- a/charms_openstack/charm/core.py
+++ b/charms_openstack/charm/core.py
@@ -16,6 +16,7 @@ import charmhelpers.core.templating
 import charmhelpers.core.unitdata as unitdata
 import charmhelpers.fetch as fetch
 import charms.reactive as reactive
+import charms.reactive.flags as flags
 import charms.reactive.relations as relations
 
 import charms_openstack.adapters as os_adapters
@@ -735,15 +736,6 @@ class BaseOpenStackCharmActions(object):
         """Render the configuration files identified in the list passed as
         configs.
 
-        If adapters_instance is None then the self.adapters_instance is used
-        that was setup in the __init__() method.  Note, if no interfaces were
-        passed (the default) then there will be no interfaces.
-
-        TODO: need to work out how to make this function more useful - at the
-        moment, with a default setup, this function is only useful to
-        render_with_interfaces() which constructs a new adapters_instance
-        anyway.
-
         Configs may not only be loaded via OpenStack loaders but also via
         string templates passed via config options or from relation data.
         This must be explicitly declared via string_templates dict of a given
@@ -755,7 +747,16 @@ class BaseOpenStackCharmActions(object):
         :param adapters_instance: [optional] the adapters_instance to use.
         """
         if adapters_instance is None:
-            adapters_instance = self.adapters_instance
+            interfaces = []
+            for f in flags.get_flags():
+                ep_from_f = relations.endpoint_from_flag(f)
+                if ep_from_f:
+                    interfaces.append(ep_from_f)
+            try:
+                adapters_instance = self.adapters_class(interfaces,
+                                                        charm_instance=self)
+            except TypeError:
+                adapters_instance = self.adapters_class(interfaces)
 
         with self.restart_on_change():
             for conf in configs:
diff --git a/unit_tests/charms_openstack/charm/test_core.py b/unit_tests/charms_openstack/charm/test_core.py
index 4d61134..43c22d3 100644
--- a/unit_tests/charms_openstack/charm/test_core.py
+++ b/unit_tests/charms_openstack/charm/test_core.py
@@ -465,8 +465,49 @@ class TestMyOpenStackCharm(BaseOpenStackCharmTest):
         self.patch_object(chm_core.os_templating,
                           'get_loader',
                           return_value='my-loader')
-        # self.patch_target('adapter_instance', new='my-adapter')
-        self.target.render_configs(['path1'])
+        self.target.render_configs(
+            ['path1'],
+            adapters_instance=self.target.adapters_instance)
+        self.assertEqual(d[0], 1)
+        self.render.assert_called_once_with(
+            source='path1',
+            template_loader='my-loader',
+            target='path1',
+            context=mock.ANY,
+            config_template=None,
+            group='root',
+            perms=0o640,
+        )
+        # assert the context was an MyAdapter instance.
+        context = self.render.call_args_list[0][1]['context']
+        assert isinstance(context, MyAdapter)
+        self.assertEqual(context.interfaces, ['interface1', 'interface2'])
+
+    def test_render_configs_construct_adapters_instance(self):
+        # give us a way to check that the context manager was called.
+        from contextlib import contextmanager
+        d = [0]
+
+        @contextmanager
+        def fake_restart_on_change():
+            d[0] += 1
+            yield
+
+        self.patch_target('restart_on_change', new=fake_restart_on_change)
+        self.patch_object(chm_core.charmhelpers.core.templating, 'render')
+        self.patch_object(chm_core.os_templating,
+                          'get_loader',
+                          return_value='my-loader')
+        self.patch_object(
+            chm_core.flags,
+            'get_flags',
+            return_value=['interface1.available', 'interface2.ready'])
+        self.patch_object(
+            chm_core.relations,
+            'endpoint_from_flag',
+            side_effect=lambda x: x.split('.')[0])
+        self.target.render_configs(
+            ['path1'])
         self.assertEqual(d[0], 1)
         self.render.assert_called_once_with(
             source='path1',
@@ -505,7 +546,9 @@ class TestMyOpenStackCharm(BaseOpenStackCharmTest):
         adapters_instance.options = mock.MagicMock()
         adapters_instance.options.t_prop = config_template
 
-        self.target.render_configs(['path1'])
+        self.target.render_configs(
+            ['path1'],
+            adapters_instance=self.target.adapters_instance)
         self.assertEqual(d[0], 1)
         self.render.assert_called_once_with(
             source='path1',
@@ -534,7 +577,10 @@ class TestMyOpenStackCharm(BaseOpenStackCharmTest):
             os_adapters.ConfigurationAdapter
         )
 
-        self.assertRaises(RuntimeError, self.target.render_configs, ['path1'])
+        self.assertRaises(
+            RuntimeError,
+            self.target.render_configs, ['path1'],
+            adapters_instance=self.target.adapters_instance)
 
     def test_render_config_from_string_no_relation(self):
         """
@@ -554,7 +600,9 @@ class TestMyOpenStackCharm(BaseOpenStackCharmTest):
 
             adapters_instance = self.target.adapters_instance
 
-            self.target.render_configs(['path1'])
+            self.target.render_configs(
+                ['path1'],
+                adapters_instance=adapters_instance)
             m.assert_called_once_with('path1', adapters_instance)
             self.render.assert_not_called()