diff --git a/domain/sap10_calculator/worksheet/tests/test_solar_gains.py b/domain/sap10_calculator/worksheet/tests/test_solar_gains.py
index 0374ce2c..3f368fa2 100644
--- a/domain/sap10_calculator/worksheet/tests/test_solar_gains.py
+++ b/domain/sap10_calculator/worksheet/tests/test_solar_gains.py
@@ -232,9 +232,11 @@ def test_ne_and_nw_share_table_u5_constants() -> None:
     sw = surface_solar_flux_w_per_m2(orientation=Orientation.SW, pitch_deg=90.0, region=0, month=4)
 
     # Assert
-    assert ne == pytest.approx(nw, abs=0.01)
-    assert e == pytest.approx(w, abs=0.01)
-    assert se == pytest.approx(sw, abs=0.01)
+    # Table U5 column-sharing — values are identical (same dictionary
+    # lookup), not approximately equal. Pin at exact equality.
+    assert ne == nw
+    assert e == w
+    assert se == sw
 
 
 def test_window_solar_gain_applies_equation_5() -> None: