diff --git a/ops/testing.py b/ops/testing.py
index d57652a9c..94b238ae9 100755
--- a/ops/testing.py
+++ b/ops/testing.py
@@ -47,7 +47,6 @@
 from io import BytesIO, StringIO
 from textwrap import dedent
 
-import ops.model
 from ops import charm, framework, model, pebble, storage
 from ops._private import yaml
 
@@ -650,7 +649,8 @@ def add_relation_unit(self, relation_id: int, remote_unit_name: str) -> None:
             None
         """
         self._backend._relation_list_map[relation_id].append(remote_unit_name)
-        self._backend._relation_data[relation_id][remote_unit_name] = {}
+        rel_data = self._backend._relation_data
+        rel_data[relation_id][remote_unit_name] = _TestingRelationDataContents()
         # TODO: jam 2020-08-03 This is where we could assert that the unit name matches the
         #  application name (eg you don't have a relation to 'foo' but add units of 'bar/0'
         self._backend._relation_app_and_units[relation_id]["units"].append(remote_unit_name)
diff --git a/test/test_testing.py b/test/test_testing.py
index 90be8b1f1..3028b5454 100644
--- a/test/test_testing.py
+++ b/test/test_testing.py
@@ -30,7 +30,7 @@
 import yaml
 
 import ops.testing
-from ops import pebble, model
+from ops import model, pebble
 from ops.charm import (
     CharmBase,
     PebbleReadyEvent,