diff --git a/changelog.d/8072.misc b/changelog.d/8072.misc
new file mode 100644
index 000000000..e26764dea
--- /dev/null
+++ b/changelog.d/8072.misc
@@ -0,0 +1 @@
+ Convert various parts of the codebase to async/await.
diff --git a/tests/federation/test_complexity.py b/tests/federation/test_complexity.py
index b8ca11871..9bd515080 100644
--- a/tests/federation/test_complexity.py
+++ b/tests/federation/test_complexity.py
@@ -79,9 +79,11 @@ class RoomComplexityTests(unittest.FederatingHomeserverTestCase):
         fed_transport = self.hs.get_federation_transport_client()
 
         # Mock out some things, because we don't want to test the whole join
-        fed_transport.client.get_json = Mock(return_value=make_awaitable({"v1": 9999}))
+        fed_transport.client.get_json = Mock(
+            side_effect=lambda *args, **kwargs: make_awaitable({"v1": 9999})
+        )
         handler.federation_handler.do_invite_join = Mock(
-            return_value=make_awaitable(("", 1))
+            side_effect=lambda *args, **kwargs: make_awaitable(("", 1))
         )
 
         d = handler._remote_join(
@@ -110,9 +112,11 @@ class RoomComplexityTests(unittest.FederatingHomeserverTestCase):
         fed_transport = self.hs.get_federation_transport_client()
 
         # Mock out some things, because we don't want to test the whole join
-        fed_transport.client.get_json = Mock(return_value=make_awaitable({"v1": 9999}))
+        fed_transport.client.get_json = Mock(
+            side_effect=lambda *args, **kwargs: make_awaitable({"v1": 9999})
+        )
         handler.federation_handler.do_invite_join = Mock(
-            return_value=make_awaitable(("", 1))
+            side_effect=lambda *args, **kwargs: make_awaitable(("", 1))
         )
 
         d = handler._remote_join(
@@ -148,9 +152,11 @@ class RoomComplexityTests(unittest.FederatingHomeserverTestCase):
         fed_transport = self.hs.get_federation_transport_client()
 
         # Mock out some things, because we don't want to test the whole join
-        fed_transport.client.get_json = Mock(return_value=make_awaitable(None))
+        fed_transport.client.get_json = Mock(
+            side_effect=lambda *args, **kwargs: make_awaitable(None)
+        )
         handler.federation_handler.do_invite_join = Mock(
-            return_value=make_awaitable(("", 1))
+            side_effect=lambda *args, **kwargs: make_awaitable(("", 1))
         )
 
         # Artificially raise the complexity
@@ -204,9 +210,11 @@ class RoomComplexityAdminTests(unittest.FederatingHomeserverTestCase):
         fed_transport = self.hs.get_federation_transport_client()
 
         # Mock out some things, because we don't want to test the whole join
-        fed_transport.client.get_json = Mock(return_value=make_awaitable({"v1": 9999}))
+        fed_transport.client.get_json = Mock(
+            side_effect=lambda *args, **kwargs: make_awaitable({"v1": 9999})
+        )
         handler.federation_handler.do_invite_join = Mock(
-            return_value=make_awaitable(("", 1))
+            side_effect=lambda *args, **kwargs: make_awaitable(("", 1))
         )
 
         d = handler._remote_join(
@@ -234,9 +242,11 @@ class RoomComplexityAdminTests(unittest.FederatingHomeserverTestCase):
         fed_transport = self.hs.get_federation_transport_client()
 
         # Mock out some things, because we don't want to test the whole join
-        fed_transport.client.get_json = Mock(return_value=make_awaitable({"v1": 9999}))
+        fed_transport.client.get_json = Mock(
+            side_effect=lambda *args, **kwargs: make_awaitable({"v1": 9999})
+        )
         handler.federation_handler.do_invite_join = Mock(
-            return_value=make_awaitable(("", 1))
+            side_effect=lambda *args, **kwargs: make_awaitable(("", 1))
         )
 
         d = handler._remote_join(