diff --git a/layers/building/building.sql b/layers/building/building.sql
index 14a48df..95f729c 100644
--- a/layers/building/building.sql
+++ b/layers/building/building.sql
@@ -13,7 +13,7 @@ END;
 $$ STRICT
 LANGUAGE plpgsql IMMUTABLE;
 
-CREATE INDEX IF NOT EXISTS osm_building_relation_building_idx ON osm_building_relation(building) WHERE ST_GeometryType(geometry) = 'ST_Polygon';
+CREATE INDEX IF NOT EXISTS osm_building_relation_building_idx ON osm_building_relation(building) WHERE building = '' AND ST_GeometryType(geometry) = 'ST_Polygon';
 CREATE INDEX IF NOT EXISTS osm_building_relation_member_idx ON osm_building_relation(member);
 --CREATE INDEX IF NOT EXISTS osm_building_associatedstreet_role_idx ON osm_building_associatedstreet(role) WHERE ST_GeometryType(geometry) = 'ST_Polygon';
 --CREATE INDEX IF NOT EXISTS osm_building_street_role_idx ON osm_building_street(role) WHERE ST_GeometryType(geometry) = 'ST_Polygon';