diff --git a/tests/rest/client/test_sendtodevice.py b/tests/rest/client/test_sendtodevice.py
index 7718e323d0..5f418c3465 100644
--- a/tests/rest/client/test_sendtodevice.py
+++ b/tests/rest/client/test_sendtodevice.py
@@ -20,14 +20,10 @@
 #
 from parameterized import parameterized_class
 
-from twisted.test.proto_helpers import MemoryReactor
-
 from synapse.api.constants import EduTypes
 from synapse.rest import admin
 from synapse.rest.client import login, sendtodevice, sync
-from synapse.server import HomeServer
 from synapse.types import JsonDict
-from synapse.util import Clock
 
 from tests.unittest import HomeserverTestCase, override_config
 
@@ -48,10 +44,13 @@ class SendToDeviceTestCase(HomeserverTestCase):
     Test `/sendToDevice` will deliver messages across to people receiving them over `/sync`.
 
     Attributes:
-        sync_endpoint (str): The endpoint under test to use for syncing.
-        experimental_features (JsonDict): The experimental features homeserver config to use.
+        sync_endpoint: The endpoint under test to use for syncing.
+        experimental_features: The experimental features homeserver config to use.
     """
 
+    sync_endpoint: str
+    experimental_features: JsonDict
+
     servlets = [
         admin.register_servlets,
         login.register_servlets,
@@ -61,14 +60,8 @@ class SendToDeviceTestCase(HomeserverTestCase):
 
     def default_config(self) -> JsonDict:
         config = super().default_config()
-        config["experimental_features"] = self.experimental_features  # type: ignore[attr-defined]
         return config
 
-    def prepare(self, reactor: MemoryReactor, clock: Clock, hs: HomeServer) -> None:
-        # This pointless re-assignment avoids `# type: ignore[attr-defined]` problems
-        # throughout the test cases
-        self.sync_endpoint: str = self.sync_endpoint
-
     def test_user_to_user(self) -> None:
         """A to-device message from one user to another should get delivered"""
 
diff --git a/tests/rest/client/test_sync.py b/tests/rest/client/test_sync.py
index a09d714e40..daeb1d3ddd 100644
--- a/tests/rest/client/test_sync.py
+++ b/tests/rest/client/test_sync.py
@@ -704,10 +704,13 @@ class DeviceListSyncTestCase(unittest.HomeserverTestCase):
     Tests regarding device list (`device_lists`) changes.
 
     Attributes:
-        sync_endpoint (str): The endpoint under test to use for syncing.
-        experimental_features (JsonDict): The experimental features homeserver config to use.
+        sync_endpoint: The endpoint under test to use for syncing.
+        experimental_features: The experimental features homeserver config to use.
     """
 
+    sync_endpoint: str
+    experimental_features: JsonDict
+
     servlets = [
         synapse.rest.admin.register_servlets,
         login.register_servlets,
@@ -718,14 +721,9 @@ class DeviceListSyncTestCase(unittest.HomeserverTestCase):
 
     def default_config(self) -> JsonDict:
         config = super().default_config()
-        config["experimental_features"] = self.experimental_features  # type: ignore[attr-defined]
+        config["experimental_features"] = self.experimental_features
         return config
 
-    def prepare(self, reactor: MemoryReactor, clock: Clock, hs: HomeServer) -> None:
-        # This pointless re-assignment avoids `# type: ignore[attr-defined]` problems
-        # throughout the test cases
-        self.sync_endpoint: str = self.sync_endpoint
-
     def test_receiving_local_device_list_changes(self) -> None:
         """Tests that a local users that share a room receive each other's device list
         changes.
@@ -917,10 +915,13 @@ class DeviceOneTimeKeysSyncTestCase(unittest.HomeserverTestCase):
     Tests regarding device one time keys (`device_one_time_keys_count`) changes.
 
     Attributes:
-        sync_endpoint (str): The endpoint under test to use for syncing.
-        experimental_features (JsonDict): The experimental features homeserver config to use.
+        sync_endpoint: The endpoint under test to use for syncing.
+        experimental_features: The experimental features homeserver config to use.
     """
 
+    sync_endpoint: str
+    experimental_features: JsonDict
+
     servlets = [
         synapse.rest.admin.register_servlets,
         login.register_servlets,
@@ -930,14 +931,10 @@ class DeviceOneTimeKeysSyncTestCase(unittest.HomeserverTestCase):
 
     def default_config(self) -> JsonDict:
         config = super().default_config()
-        config["experimental_features"] = self.experimental_features  # type: ignore[attr-defined]
+        config["experimental_features"] = self.experimental_features
         return config
 
     def prepare(self, reactor: MemoryReactor, clock: Clock, hs: HomeServer) -> None:
-        # This pointless re-assignment avoids `# type: ignore[attr-defined]` problems
-        # throughout the test cases
-        self.sync_endpoint: str = self.sync_endpoint
-
         self.e2e_keys_handler = hs.get_e2e_keys_handler()
 
     def test_no_device_one_time_keys(self) -> None:
@@ -1029,10 +1026,13 @@ class DeviceUnusedFallbackKeySyncTestCase(unittest.HomeserverTestCase):
     Tests regarding device one time keys (`device_unused_fallback_key_types`) changes.
 
     Attributes:
-        sync_endpoint (str): The endpoint under test to use for syncing.
-        experimental_features (JsonDict): The experimental features homeserver config to use.
+        sync_endpoint: The endpoint under test to use for syncing.
+        experimental_features: The experimental features homeserver config to use.
     """
 
+    sync_endpoint: str
+    experimental_features: JsonDict
+
     servlets = [
         synapse.rest.admin.register_servlets,
         login.register_servlets,
@@ -1042,14 +1042,10 @@ class DeviceUnusedFallbackKeySyncTestCase(unittest.HomeserverTestCase):
 
     def default_config(self) -> JsonDict:
         config = super().default_config()
-        config["experimental_features"] = self.experimental_features  # type: ignore[attr-defined]
+        config["experimental_features"] = self.experimental_features
         return config
 
     def prepare(self, reactor: MemoryReactor, clock: Clock, hs: HomeServer) -> None:
-        # This pointless re-assignment avoids `# type: ignore[attr-defined]` problems
-        # throughout the test cases
-        self.sync_endpoint: str = self.sync_endpoint
-
         self.store = self.hs.get_datastores().main
         self.e2e_keys_handler = hs.get_e2e_keys_handler()