diff --git a/tests/domain/epc_prediction/test_validation.py b/tests/domain/epc_prediction/test_validation.py
index 2cdad977..24fa0198 100644
--- a/tests/domain/epc_prediction/test_validation.py
+++ b/tests/domain/epc_prediction/test_validation.py
@@ -64,6 +64,10 @@ def _comparable(
     heating.cylinder_insulation_type = 1
     heating.secondary_heating_type = None
     epc.sap_heating = heating
+    # Display heating rows the heating-donor synthesis carries (ADR-0029
+    # follow-up); `main_heating` has no dataclass default, so a partial instance
+    # must set it. `main_heating_controls` / `sap_ventilation` default to None.
+    epc.main_heating = []
     energy: SapEnergySource = object.__new__(SapEnergySource)
     energy.photovoltaic_supply = None
     energy.photovoltaic_arrays = None