diff --git a/tests/domain/epc/test_glazing_mix_guard.py b/tests/domain/epc/test_glazing_mix_guard.py
index 973b96b6a..04e351cd3 100644
--- a/tests/domain/epc/test_glazing_mix_guard.py
+++ b/tests/domain/epc/test_glazing_mix_guard.py
@@ -1,5 +1,7 @@
 from __future__ import annotations
 
+import pytest
+
 from domain.epc.property_overrides.glazing_type import GlazingType
 from domain.epc.property_overrides.glazing_mix_guard import glazing_mix_guard
 
@@ -14,3 +16,24 @@ def test_a_genuine_percentage_mix_classifies_as_mixed() -> None:
     # Assert — a mix defers to the cert's per-window glazing, not a whole-dwelling
     # type.
     assert result is GlazingType.MIXED
+
+
+@pytest.mark.parametrize(
+    "description",
+    [
+        "100% double glazing 2002 or later",  # uniform — one type
+        "96% double glazing 2002 or later, 4% single glazing",  # >= 90% -> uniform
+        "80% double glazing 2002 or later, 20% double glazing pre-2002",  # same base type
+        "some double glazing and a bit of single",  # unparseable — no percentages
+        "",
+    ],
+)
+def test_uniform_or_unparseable_glazing_defers_to_the_llm(description: str) -> None:
+    # The guard only claims a genuine percentage mix; a uniform assertion (applied
+    # as that type) or a varied phrasing is left for the LLM classifier.
+
+    # Act
+    result = glazing_mix_guard(description)
+
+    # Assert
+    assert result is None