diff --git a/etl/filter_mastermap.py b/etl/filter_mastermap.py
index 3315a6ca..66108b78 100644
--- a/etl/filter_mastermap.py
+++ b/etl/filter_mastermap.py
@@ -19,8 +19,7 @@ def main(mastermap_path):
 
 
 def filter_mastermap(mm_path):
-    output_path = "{}.filtered.csv"
-    output_path.format(str(mm_path).replace(".gml.csv", ""))
+    output_path = "{}.filtered.csv".format(str(mm_path).replace(".gml.csv", ""))
     output_fieldnames = ('WKT', 'fid', 'descriptiveGroup')
     # Open the input csv with all polygons, buildings and others
     with open(mm_path, 'r') as fh:
diff --git a/tests/test_mastermap.filtered.csv b/tests/test_mastermap.filtered.csv
index 28cc7baf..286b40b3 100644
--- a/tests/test_mastermap.filtered.csv
+++ b/tests/test_mastermap.filtered.csv
@@ -1,2 +1,3 @@
 WKT,fid,descriptiveGroup
 "POLYGON ((484704.003 184721.2,484691.62 184729.971,484688.251 184725.214,484700.633 184716.443,484704.003 184721.2))",osgb5000005129953843,"[ ""Building"" ]"
+"POLYGON ((530022.138 177486.29,530043.695 177498.235,530043.074 177499.355,530042.435 177500.509,530005.349 177480.086,529978.502 177463.333,529968.87 177457.322,529968.446 177457.057,529968.199 177455.714,529968.16 177455.504,529966.658 177454.566,529958.613 177449.543,529956.624 177448.301,529956.62 177448.294,529956.08 177447.4,529954.238 177444.351,529953.197 177442.624,529953.186 177442.609,529950.768 177438.606,529950.454 177438.086,529949.47 177434.209,529950.212 177434.038,529954.216 177433.114,529955.098 177437.457,529952.714 177437.98,529953.55 177441.646,529953.842 177442.008,529957.116 177446.059,529957.449 177446.471,529968.508 177453.375,529974.457 177451.966,529976.183 177458.937,530003.157 177475.772,530020.651 177485.466,530021.257 177484.372,530022.744 177485.196,530022.138 177486.29))",osgb5000005283023887,"[ ""Building"" ]"