diff --git a/tests/domain/modelling/test_wall_recommendation.py b/tests/domain/modelling/test_wall_recommendation.py
index b47d9eb16..8fe2620d4 100644
--- a/tests/domain/modelling/test_wall_recommendation.py
+++ b/tests/domain/modelling/test_wall_recommendation.py
@@ -90,6 +90,28 @@ def test_non_cavity_main_wall_yields_no_recommendation() -> None:
     assert recommendation is None
 
 
+def test_at_regs_age_band_wall_yields_no_solid_wall_recommendation() -> None:
+    # Arrange — a timber-frame wall lodged as-built at construction age band L
+    # (2012-2022). RdSAP's cascade assigns it the at-regs U-value (0.28), and
+    # 100 mm IWI resolves to the SAME value — the measure cannot change the
+    # modelled wall, so offering it sells £4k of insulation for +0.00 SAP
+    # (property 711795, PRD #1435 WS2). The Wall U-Value Gate withholds it
+    # (ADR-0051).
+    baseline: EpcPropertyData = build_epc()
+    main: SapBuildingPart = _part(baseline, BuildingPartIdentifier.MAIN)
+    main.wall_construction = 5  # timber frame — IWI-only construction
+    main.wall_insulation_type = 4  # as-built / uninsulated — the legacy trigger
+    main.construction_age_band = "L"
+
+    # Act
+    recommendation: Recommendation | None = recommend_solid_wall(
+        baseline, _StubProducts()
+    )
+
+    # Assert
+    assert recommendation is None
+
+
 def test_park_home_wall_yields_no_solid_wall_recommendation() -> None:
     # Arrange — a park home (wall_construction code 8) with an uninsulated
     # as-built wall. Code 8 is NOT system-built (ADR-0019); a park home's