diff --git a/lerobot/common/datasets/lerobot_dataset.py b/lerobot/common/datasets/lerobot_dataset.py
index 7c61e486..dddd11ab 100644
--- a/lerobot/common/datasets/lerobot_dataset.py
+++ b/lerobot/common/datasets/lerobot_dataset.py
@@ -736,7 +736,7 @@ class LeRobotDataset(torch.utils.data.Dataset):
         for key in self.meta.video_keys:
             if query_indices is not None and key in query_indices:
                 timestamps = self.hf_dataset.select(query_indices[key])["timestamp"]
-                query_timestamps[key] = timestamps.tolist()
+                query_timestamps[key] = torch.stack(timestamps).tolist()
             else:
                 query_timestamps[key] = [current_ts]
 
@@ -744,7 +744,7 @@ class LeRobotDataset(torch.utils.data.Dataset):
 
     def _query_hf_dataset(self, query_indices: dict[str, list[int]]) -> dict:
         return {
-            key: self.hf_dataset.select(q_idx)[key]
+            key: torch.stack(self.hf_dataset.select(q_idx)[key])
             for key, q_idx in query_indices.items()
             if key not in self.meta.video_keys
         }
diff --git a/tests/datasets/test_delta_timestamps.py b/tests/datasets/test_delta_timestamps.py
index d2ca7d13..35014642 100644
--- a/tests/datasets/test_delta_timestamps.py
+++ b/tests/datasets/test_delta_timestamps.py
@@ -56,8 +56,8 @@ def calculate_episode_data_index(hf_dataset: datasets.Dataset) -> dict[str, np.n
 def synced_timestamps_factory(hf_dataset_factory):
     def _create_synced_timestamps(fps: int = 30) -> tuple[np.ndarray, np.ndarray, np.ndarray]:
         hf_dataset = hf_dataset_factory(fps=fps)
-        timestamps = hf_dataset["timestamp"].numpy()
-        episode_indices = hf_dataset["episode_index"].numpy()
+        timestamps = torch.stack(hf_dataset["timestamp"]).numpy()
+        episode_indices = torch.stack(hf_dataset["episode_index"]).numpy()
         episode_data_index = calculate_episode_data_index(hf_dataset)
         return timestamps, episode_indices, episode_data_index