diff --git a/src/genet/schedule_elements.py b/src/genet/schedule_elements.py
index d99e4a55..a9274f9d 100644
--- a/src/genet/schedule_elements.py
+++ b/src/genet/schedule_elements.py
@@ -3698,7 +3698,7 @@ def write_to_json(self, output_dir: str):
             json.dump(self.to_json(), outfile)
         self.write_extras(output_dir)
 
-    def write_spatial(self, output_dir, epsg: str = None, filetype: Optional[str] = "parquet"):
+    def write_spatial(self, output_dir, epsg: str = None, filetype: str = "parquet"):
         """Transforms Schedule (if applicable) to geopandas.GeoDataFrame of nodes and links and saves to
         the requested file format.
 
diff --git a/src/genet/utils/io.py b/src/genet/utils/io.py
index b2559f2b..00faece8 100644
--- a/src/genet/utils/io.py
+++ b/src/genet/utils/io.py
@@ -4,8 +4,8 @@
 import geopandas as gpd
 from pandas.core.dtypes.common import is_datetime64_any_dtype as is_datetime
 
-from genet.output import sanitiser as sanitiser
-from genet.utils import persistence as persistence
+from genet.output import sanitiser
+from genet.utils import persistence
 
 SUPPORTED_FILE_FORMATS = ["parquet", "geoparquet", "geojson", "shp", "shapefile"]
 
@@ -26,7 +26,7 @@ def check_file_type_is_supported(filetype: str):
 
 
 def save_geodataframe(
-    gdf: gpd.GeoDataFrame, filename: str, output_dir: str, filetype: Optional[str] = "parquet"
+    gdf: gpd.GeoDataFrame, filename: str, output_dir: str, filetype: str = "parquet"
 ):
     """Saves geopandas.GeoDataFrame to the requested file format