diff --git a/tests/domain/epc/test_main_heating_system_overlay.py b/tests/domain/epc/test_main_heating_system_overlay.py
index d7c500f53..7bd0db524 100644
--- a/tests/domain/epc/test_main_heating_system_overlay.py
+++ b/tests/domain/epc/test_main_heating_system_overlay.py
@@ -419,3 +419,20 @@ def test_solid_fuel_room_heater_drags_its_coherent_room_heater_companions() -> N
     assert heating.main_heating_category == 10
     assert heating.main_heating_control == 2601
     assert heating.meter_type == "Single"
+
+
+def test_electric_room_heaters_drag_their_natural_electricity_fuel() -> None:
+    # A landlord names the system; an electric room heater's natural fuel is
+    # unambiguously electricity (RdSAP main_fuel code 29). The overlay drags it so
+    # a system-only override is self-coherent even on a cert that lodged a
+    # different fuel — a later `main_fuel` override still wins (last-wins
+    # composition), and a contradicting fuel is logged, not silently kept
+    # (ADR-0041 natural-fuel coherence).
+
+    # Act
+    simulation = main_heating_overlay_for("Electric room heaters", 0)
+
+    # Assert
+    assert simulation is not None
+    assert simulation.heating is not None
+    assert simulation.heating.main_fuel_type == 29