diff --git a/backend/pashub_fetcher/tests/test_core_files.py b/backend/pashub_fetcher/tests/test_core_files.py
index f968a976..c6970def 100644
--- a/backend/pashub_fetcher/tests/test_core_files.py
+++ b/backend/pashub_fetcher/tests/test_core_files.py
@@ -108,3 +108,14 @@ def test_core_file_for_evidence_category_returns_retrofit_design_doc() -> None:
 
     # Assert
     assert result == CoreFiles.RETROFIT_DESIGN_DOC
+
+
+def test_core_file_for_ioe_substring_returns_improvement_option_evaluation() -> None:
+    # Arrange
+    filename = "6000802 - NG4 4HD - Improvement Option Evaluation.pdf"
+
+    # Act
+    result = core_file_for(filename)
+
+    # Assert
+    assert result == CoreFiles.IMPROVEMENT_OPTION_EVALUATION