diff --git a/etl/filter_mastermap.py b/etl/filter_mastermap.py
index de4a02d0..2167a53c 100644
--- a/etl/filter_mastermap.py
+++ b/etl/filter_mastermap.py
@@ -14,6 +14,7 @@ csv.field_size_limit(sys.maxsize)
 def main(mastermap_path):
     mm_paths = sorted(glob.glob(os.path.join(mastermap_path, "*.gml.csv")))
     for mm_path in mm_paths:
+        print(mm_path)
         filter_mastermap(mm_path)
 
 
@@ -28,8 +29,11 @@ def filter_mastermap(mm_path):
             w = csv.DictWriter(output_fh, fieldnames=output_fieldnames)
             w.writeheader()
             for line in r:
-                if 'Building' in line['descriptiveGroup']:
-                    w.writerow(line)
+                try:
+                    if 'Building' in line['descriptiveGroup']:
+                        w.writerow(line)
+                except TypeError:  # when descriptiveGroup is missing, ignore this Polygon
+                    pass
 
 
 if __name__ == '__main__':
diff --git a/tests/test_filter.py b/tests/test_filter.py
index aae7842d..16284657 100644
--- a/tests/test_filter.py
+++ b/tests/test_filter.py
@@ -7,17 +7,17 @@ def test_filter_mastermap():
     """Test that MasterMap CSV can be correctly filtered to include only buildings."""
     input_file = "tests/test_mastermap.gml.csv"  # Test csv with one building and one non-building
     output_file = input_file.replace('gml', 'filtered')
-    filter_mastermap(input_file)  # creates test_mastermap.filtered.csv
+    filter_mastermap(input_file)  # creates output_file
     with open(output_file, newline='') as csvfile:
         csv_array = list(csv.reader(csvfile))
     assert len(csv_array) == 2  # assert that length is 2 because just one row after header
     
     
-def test_filter_mastermap_missing_type():
+def test_filter_mastermap_missing_descriptivegroup():
     """Test that MasterMap CSV can be correctly filtered when the polygon does not have a type specified."""
-    input_file = "tests/test_mastermap_missing_type.gml.csv"  # Test csv with one building and one non-building
+    input_file = "tests/test_mastermap_missing_descriptivegroup.gml.csv"  # Test csv with one building and one non-building
     output_file = input_file.replace('gml', 'filtered')
-    filter_mastermap(input_file)  # creates test_mastermap.filtered.csv
+    filter_mastermap(input_file)  # creates output_file
     with open(output_file, newline='') as csvfile:
         csv_array = list(csv.reader(csvfile))
-    assert len(csv_array) == 2  # assert that length is 2 because just one row after header
\ No newline at end of file
+    assert len(csv_array) == 1  # assert that length is 1 because just header
\ No newline at end of file
diff --git a/tests/test_mastermap_missing_descriptivegroup.filtered.csv b/tests/test_mastermap_missing_descriptivegroup.filtered.csv
new file mode 100644
index 00000000..8de75769
--- /dev/null
+++ b/tests/test_mastermap_missing_descriptivegroup.filtered.csv
@@ -0,0 +1 @@
+WKT,fid,descriptiveGroup
diff --git a/tests/test_mastermap_missing_type.gml.csv b/tests/test_mastermap_missing_descriptivegroup.gml.csv
similarity index 100%
rename from tests/test_mastermap_missing_type.gml.csv
rename to tests/test_mastermap_missing_descriptivegroup.gml.csv