diff --git a/tests/domain/epc/test_main_heating_system_overlay.py b/tests/domain/epc/test_main_heating_system_overlay.py
index 804183a3b..d8431e7ef 100644
--- a/tests/domain/epc/test_main_heating_system_overlay.py
+++ b/tests/domain/epc/test_main_heating_system_overlay.py
@@ -555,3 +555,31 @@ def test_oil_room_heater_drags_its_coherent_room_heater_companions() -> None:
     assert heating.main_heating_control == 2601
     assert heating.main_fuel_type == 28
     assert heating.meter_type == "Single"
+
+
+@pytest.mark.parametrize(
+    ("value", "code"),
+    [
+        ("Gas room heater, condensing fire", 611),
+        ("Gas room heater, decorative fuel-effect", 612),
+        ("Gas room heater, flush live-effect", 605),
+        ("Gas room heater, open flue 1980 or later", 603),
+        ("Gas room heater, open flue pre-1980", 601),
+    ],
+)
+def test_gas_room_heater_variants_decode_to_their_sap_codes(
+    value: str, code: int
+) -> None:
+    # Gas room heaters span a wide efficiency range (decorative 0.20 -> condensing
+    # 0.85), so each catalogue variant maps to its own SAP Table 4a code rather
+    # than collapsing to one representative — which would over-credit a decorative
+    # fire and under-credit a condensing one. Today they mis-bucket to "Gas
+    # boiler, regular" (ADR-0041).
+
+    # Act
+    simulation = main_heating_overlay_for(value, 0)
+
+    # Assert
+    assert simulation is not None
+    assert simulation.heating is not None
+    assert simulation.heating.sap_main_heating_code == code