diff --git a/gnpy/example-data/write_path_jsontocsv.py b/gnpy/example-data/write_path_jsontocsv.py
index 7d56160a..e05538d3 100644
--- a/gnpy/example-data/write_path_jsontocsv.py
+++ b/gnpy/example-data/write_path_jsontocsv.py
@@ -19,8 +19,8 @@ from gnpy.topology.request import jsontocsv
 
 
 parser = ArgumentParser(description='Converting JSON path results into a CSV')
-parser.add_argument('filename', nargs='?', type=Path)
-parser.add_argument('output_filename', nargs='?', type=Path)
+parser.add_argument('filename', type=Path)
+parser.add_argument('output_filename', type=Path)
 parser.add_argument('eqpt_filename', nargs='?', type=Path, default=Path(__file__).parent / 'eqpt_config.json')
 
 if __name__ == '__main__':