diff --git a/tests/handlers/test_appservice.py b/tests/handlers/test_appservice.py
index 08a4ab624a..a649f512e6 100644
--- a/tests/handlers/test_appservice.py
+++ b/tests/handlers/test_appservice.py
@@ -77,6 +77,7 @@ class AppServiceHandlerTestCase(unittest.TestCase):
         self.reactor, self.clock = get_clock()
 
         hs = Mock()
+        hs.hostname = "test_server"
 
         def test_run_as_background_process(
             desc: "LiteralString",
diff --git a/tests/storage/test_base.py b/tests/storage/test_base.py
index 577229c119..e67d36cf63 100644
--- a/tests/storage/test_base.py
+++ b/tests/storage/test_base.py
@@ -105,7 +105,7 @@ class SQLBaseStoreTestCase(unittest.TestCase):
         # To fix isinstance(...) checks.
         fake_engine.__class__ = engine.__class__  # type: ignore[assignment]
 
-        db = DatabasePool(Mock(), Mock(config=db_config), fake_engine)
+        db = DatabasePool(Mock(hostname="test"), Mock(config=db_config), fake_engine)
         db._db_pool = conn_pool
 
         self.datastore = SQLBaseStore(db, None, hs)  # type: ignore[arg-type]
diff --git a/tests/test_state.py b/tests/test_state.py
index b69a09dab5..d2e50cf94b 100644
--- a/tests/test_state.py
+++ b/tests/test_state.py
@@ -245,6 +245,7 @@ class StateTestCase(unittest.TestCase):
         )
         reactor, clock = get_clock()
         hs.config = default_config(server_name="tesths", parse=True)
+        hs.hostname = "tesths"
         hs.get_datastores.return_value = Mock(
             main=self.dummy_store,
             state_deletion=dummy_deletion_store,