diff --git a/mlair/data_handler/data_handler_single_station.py b/mlair/data_handler/data_handler_single_station.py
index 360ab6408345de83c21ee5d29031b3b5f131525b..9d274558e3805334cd706fe4e2c9a914ad6e5f58 100644
--- a/mlair/data_handler/data_handler_single_station.py
+++ b/mlair/data_handler/data_handler_single_station.py
@@ -53,7 +53,7 @@ class DataHandlerSingleStation(AbstractDataHandler):
 
     _hash = ["station", "statistics_per_var", "data_origin", "station_type", "network", "sampling", "target_dim",
              "target_var", "time_dim", "iter_dim", "window_dim", "window_history_size", "window_history_offset",
-             "window_lead_time", "interpolation_limit", "interpolation_method"]
+             "window_lead_time", "interpolation_limit", "interpolation_method", "variables"]
 
     def __init__(self, station, data_path, statistics_per_var=None, station_type=DEFAULT_STATION_TYPE,
                  network=DEFAULT_NETWORK, sampling: Union[str, Tuple[str]] = DEFAULT_SAMPLING,
diff --git a/mlair/data_handler/iterator.py b/mlair/data_handler/iterator.py
index f2e3b689512ee99524eef8445f84a5a3bdb60f90..e353f84d85a0871b00964899efb2a79bf555aefc 100644
--- a/mlair/data_handler/iterator.py
+++ b/mlair/data_handler/iterator.py
@@ -9,6 +9,7 @@ import math
 import os
 import shutil
 import pickle
+import logging
 import dill
 from typing import Tuple, List
 
@@ -142,6 +143,7 @@ class KerasIterator(keras.utils.Sequence):
         remaining = None
         mod_rank = self._get_model_rank()
         for data in self._collection:
+            logging.debug(f"prepare batches for {str(data)}")
             X = data.get_X(upsampling=self.upsampling)
             Y = [data.get_Y(upsampling=self.upsampling)[0] for _ in range(mod_rank)]
             if self.upsampling: