diff --git a/src/genet/core.py b/src/genet/core.py
index 05d562e4..df40f14f 100644
--- a/src/genet/core.py
+++ b/src/genet/core.py
@@ -3015,7 +3015,7 @@ def write_to_json(self, output_dir: str):
             self.schedule.write_to_json(output_dir)
         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: Optional[str] = None, filetype: str = "parquet"):
         """Transforms Network and Schedule (if applicable) to geopandas.GeoDataFrame of nodes and links and saves to
         the requested file format.
 
diff --git a/src/genet/output/spatial.py b/src/genet/output/spatial.py
index 3f65d472..98831c9c 100644
--- a/src/genet/output/spatial.py
+++ b/src/genet/output/spatial.py
@@ -3,7 +3,6 @@
 import math
 import os
 from itertools import chain
-from typing import Optional
 
 import geopandas as gpd
 import pandas as pd
@@ -63,8 +62,8 @@ def line_geometry():
 def generate_standard_outputs_for_schedule(
     schedule,
     output_dir: str,
-    gtfs_day: Optional[str] = "19700101",
-    filetype: Optional[str] = "parquet",
+    gtfs_day: str = "19700101",
+    filetype: str = "parquet",
     schedule_network_factor=1.3,
     gdf_network_links=None,
 ):
@@ -204,11 +203,7 @@ def generate_standard_outputs_for_schedule(
 
 
 def generate_standard_outputs(
-    n,
-    output_dir,
-    gtfs_day="19700101",
-    filetype: Optional[str] = "parquet",
-    schedule_network_factor=1.3,
+    n, output_dir, gtfs_day="19700101", filetype: str = "parquet", schedule_network_factor=1.3
 ):
     """Generates spatial files that can be used for generating standard visualisations.
 
diff --git a/src/genet/schedule_elements.py b/src/genet/schedule_elements.py
index a9274f9d..e8b126e3 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: str = "parquet"):
+    def write_spatial(self, output_dir, epsg: Optional[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 00faece8..fb98da68 100644
--- a/src/genet/utils/io.py
+++ b/src/genet/utils/io.py
@@ -1,5 +1,4 @@
 import os
-from typing import Optional
 
 import geopandas as gpd
 from pandas.core.dtypes.common import is_datetime64_any_dtype as is_datetime
diff --git a/tests/test_utils_io.py b/tests/test_utils_io.py
index 29623d1b..808992fd 100644
--- a/tests/test_utils_io.py
+++ b/tests/test_utils_io.py
@@ -13,6 +13,17 @@ def test_throws_error_when_filetype_is_not_supported():
     assert "is not a supported file type" in str(e.value)
 
 
+def test_saving_empty_geodataframe_does_not_produce_file(tmpdir):
+    expected_file_name = "tmp"
+    expected_output_path = tmpdir / expected_file_name + ".parquet"
+    assert not os.path.exists(expected_output_path)
+
+    gdf = GeoDataFrame(columns=["id", "geometry"])
+    genet.utils.io.save_geodataframe(gdf, filename=expected_file_name, output_dir=tmpdir)
+
+    assert not os.path.exists(expected_output_path)
+
+
 def test_saving_geodataframe_with_missing_geometry_produces_file(tmpdir):
     expected_file_name = "tmp"
     expected_output_path = tmpdir / expected_file_name + ".parquet"