diff --git a/domain/sap10_calculator/worksheet/tests/test_internal_gains.py b/domain/sap10_calculator/worksheet/tests/test_internal_gains.py
index 11298313..55bdb058 100644
--- a/domain/sap10_calculator/worksheet/tests/test_internal_gains.py
+++ b/domain/sap10_calculator/worksheet/tests/test_internal_gains.py
@@ -580,7 +580,15 @@ def _build_section_5_epc(fixture: ModuleType) -> EpcPropertyData:
     doesn't yet carry: sap_windows (DG air-filled / PVC), low-energy bulb
     count, and a MainHeatingDetail with the recorded pump age. Kept in
     test scope so the legacy fixture build_epc()s stay pinned for §1-§4
-    conformance + the e2e SAP-score regression."""
+    conformance + the e2e SAP-score regression.
+
+    Per S0380.110 the §5 lighting cascade reads per-rooflight glazing
+    via `epc.sap_roof_windows` (Appendix L §L2a per-window g_L) rather
+    than a single aggregate area + bulk g_L. Propagate the fixture's
+    lodged rooflights so `_daylight_factor_from_cert` sees Triple /
+    Double / Single distinctions for the cohort (e.g. 000516 lodges a
+    Double-glazed rooflight at 1.18 m² × g_L=0.80 × FF=0.70 × Z_L=1.0).
+    """
     def _window(area: float) -> SapWindow:
         side = area ** 0.5
         return SapWindow(
@@ -610,10 +618,12 @@ def _build_section_5_epc(fixture: ModuleType) -> EpcPropertyData:
         ],
         has_fixed_air_conditioning=False,
     )
+    fixture_epc = fixture.build_epc()
     return make_minimal_sap10_epc(
         total_floor_area_m2=fixture.LINE_4_TFA_M2,
         low_energy_fixed_lighting_bulbs_count=fixture.SECTION_5_BULB_COUNT_LEL,
         sap_windows=[_window(a) for a in fixture.SECTION_5_WINDOW_AREAS_M2],
+        sap_roof_windows=list(fixture_epc.sap_roof_windows) if fixture_epc.sap_roof_windows else None,
         sap_heating=sap_heating,
     )