diff --git a/mlair/helpers/statistics.py b/mlair/helpers/statistics.py
index a1e713a8c135800d02ff7c27894485a5da7fae37..fef52fb27d602b5931587ff0fa2d8edd7e0c2d8f 100644
--- a/mlair/helpers/statistics.py
+++ b/mlair/helpers/statistics.py
@@ -314,7 +314,10 @@ class SkillScores:
 
         :return: all CASES as well as all terms
         """
-        ahead_names = list(self.external_data[self.ahead_dim].data)
+        if self.external_data is not None:
+            ahead_names = list(self.external_data[self.ahead_dim].data)
+        else:
+            ahead_names = list(internal_data[self.ahead_dim].data)
 
         all_terms = ['AI', 'AII', 'AIII', 'AIV', 'BI', 'BII', 'BIV', 'CI', 'CIV', 'CASE I', 'CASE II', 'CASE III',
                      'CASE IV']
diff --git a/mlair/run_modules/pre_processing.py b/mlair/run_modules/pre_processing.py
index 08bff85c9c1fe06111ddb47e7a3952404e05c0ac..791b8b7b08d2a4267e22a2a7b38873c9d70f0fc1 100644
--- a/mlair/run_modules/pre_processing.py
+++ b/mlair/run_modules/pre_processing.py
@@ -268,7 +268,7 @@ class PreProcessing(RunEnvironment):
                     valid_stations.append(s)
 
         logging.info(f"run for {t_outer} to check {len(set_stations)} station(s). Found {len(collection)}/"
-                     f"{len(set_stations)} valid stations.")
+                     f"{len(set_stations)} valid stations ({set_name}).")
         if set_name == "train":
             self.store_data_handler_attributes(data_handler, collection)
         return collection, valid_stations