diff --git a/preprocess/preprocessor.py b/preprocess/preprocessor.py
index aa46a02..7cc6bf2 100644
--- a/preprocess/preprocessor.py
+++ b/preprocess/preprocessor.py
@@ -153,6 +153,7 @@ def save_scene_data(root, scene, scene_idx=0, scene_total=1,file_type="txt"):
         
         if not has_points:
             target_points = np.zeros((0, 3))
+            target_normals = np.zeros((0, 3))
             
         save_target_points(root, scene, frame_id, target_points, file_type=file_type)
         save_target_normals(root, scene, frame_id, target_normals, file_type=file_type)