diff --git a/flatland/envs/observations.py b/flatland/envs/observations.py
index bd095dba527dae03e7ccc35b09c19039119ed6c9..4476bef5ac6ed271a860a6e9071f5b803448d75a 100644
--- a/flatland/envs/observations.py
+++ b/flatland/envs/observations.py
@@ -491,7 +491,7 @@ class TreeObsForRailEnv(ObservationBuilder):
         child_size = (len(tree) - num_features_per_node) // 4
         tree_data = tree[0:num_features_per_node - 1].tolist()
         distance_data = [tree[num_features_per_node - 3]]
-        agent_data = tree[-2:]
+        agent_data = tree[-2:].tolist()
         for children in range(4):
             child_tree = tree[(num_features_per_node + children * child_size):
                               (num_features_per_node + (children + 1) * child_size)]
@@ -501,7 +501,7 @@ class TreeObsForRailEnv(ObservationBuilder):
             if len(tmp_tree_data) > 0:
                 tree_data.extend(tmp_tree_data)
                 distance_data.extend(tmp_distance_data)
-                agent_data.extrend(tmp_agent_data)
+                agent_data.extend(tmp_agent_data)
         return tree_data, distance_data, agent_data