diff --git a/datatypes/epc/domain/tests/test_from_sap_schema.py b/datatypes/epc/domain/tests/test_from_sap_schema.py
index 7a682c8d7..ec9981009 100644
--- a/datatypes/epc/domain/tests/test_from_sap_schema.py
+++ b/datatypes/epc/domain/tests/test_from_sap_schema.py
@@ -181,6 +181,7 @@ class TestFullSapElectricityTariffTranslation:
             (2, "SEVEN_HOUR"),       # off-peak 7-hour → Economy 7
             (3, "SEVEN_HOUR"),       # off-peak 10-hour → dual (§12 resolves 7/10hr)
             (4, "TWENTY_FOUR_HOUR"),  # 24-hour tariff (e.g. property 709874 — unchanged)
+            (5, "EIGHTEEN_HOUR"),    # off-peak 18-hour — was dropped to "" → STANDARD
             (None, "STANDARD"),      # absent/ND → unknown → standard
         ],
     )