diff --git a/tests/gateway/test_fast_command.py b/tests/gateway/test_fast_command.py
index 60b9949025..dc869ea17f 100644
--- a/tests/gateway/test_fast_command.py
+++ b/tests/gateway/test_fast_command.py
@@ -59,6 +59,7 @@ def _make_runner():
     runner._session_db = None
     runner._agent_cache = {}
     runner._agent_cache_lock = threading.Lock()
+    runner._session_model_overrides = {}
     runner.hooks = SimpleNamespace(loaded_hooks=False)
     runner.config = SimpleNamespace(streaming=None)
     runner.session_store = SimpleNamespace(