diff --git a/activitysim/abm/models/auto_ownership.py b/activitysim/abm/models/auto_ownership.py
index 522ff7236..b7c287937 100644
--- a/activitysim/abm/models/auto_ownership.py
+++ b/activitysim/abm/models/auto_ownership.py
@@ -36,6 +36,7 @@ def auto_ownership_simulate(
     state: workflow.State,
     households: pd.DataFrame,
     households_merged: pd.DataFrame,
+    # FIXME: persons_merged not used but included, see #853
     persons_merged: pd.DataFrame,
     model_settings: AutoOwnershipSettings | None = None,
     model_settings_file_name: str = "auto_ownership.yaml",