diff --git a/laserchicken/feature_extractor/pulse_penetration_feature_extractor.py b/laserchicken/feature_extractor/pulse_penetration_feature_extractor.py
index f9abb2d..6774be3 100644
--- a/laserchicken/feature_extractor/pulse_penetration_feature_extractor.py
+++ b/laserchicken/feature_extractor/pulse_penetration_feature_extractor.py
@@ -52,8 +52,7 @@ def extract(self, point_cloud, neighborhood, target_point_cloud, target_index, v
         :param volume_description: volume object that describes the shape and size of the search volume
         :return: feature value
         """
-        class_neighbors = np.array(point_cloud[point]['raw_classification']["data"][
-            neighborhood])
+        class_neighbors = [point_cloud[point]['raw_classification']["data"][n] for n in neighborhood]
 
         ground_indices = self._get_ground_indices(
             class_neighbors, self.ground_tags)