diff --git a/airborne_lidar/airborne_lidar_seg.py b/airborne_lidar/airborne_lidar_seg.py
index 963d5ae..c0fc587 100644
--- a/airborne_lidar/airborne_lidar_seg.py
+++ b/airborne_lidar/airborne_lidar_seg.py
@@ -451,7 +451,7 @@ def main():
             iou_csv.write(('filename', 'overall_iou', 'per_class_iou'))
             for filename in files:
                 xyzni, label, nb_pts, header = read_las_format(filename)
-                prep_filename = Path(f"{filename.parents / filename.stem}_prepared.hdfs")
+                prep_filename = Path(f"{filename.parents / Path(filename.stem)}_prepared.hdfs")
                 write_features(prep_filename, xyzni=xyzni, labels=label)
                 iou = test(args, prep_filename.stem, model_folder, prep_filename.parents, info_class, files.index(filename), header=header)
                 line = (filename.stem, f"{iou[0]:.3f}")