diff --git a/src/model_modules/linear_model.py b/src/model_modules/linear_model.py
index 3d5323e1b0303b497c1f26c4e84ee9b968380425..933a108c1b06e1786f75e7f4ebd9b220fbe812dd 100644
--- a/src/model_modules/linear_model.py
+++ b/src/model_modules/linear_model.py
@@ -31,7 +31,7 @@ class OrdinaryLeastSquaredModel:
         self.y = data_y
 
     def predict(self, data):
-        data = sm.add_constant(self.reshape_xarray_to_numpy(data))
+        data = sm.add_constant(self.reshape_xarray_to_numpy(data), has_constant="add")
         return np.atleast_2d(self.model.predict(data))
 
     @staticmethod
diff --git a/src/run_modules/model_setup.py b/src/run_modules/model_setup.py
index d2c8d93fc957ecb2990e99000cbd3588e2d83eef..32ca0d2e82af32d8164d80ac42731e10f431a458 100644
--- a/src/run_modules/model_setup.py
+++ b/src/run_modules/model_setup.py
@@ -100,5 +100,5 @@ class ModelSetup(RunEnvironment):
 
     def plot_model(self):  # pragma: no cover
         with tf.device("/cpu:0"):
-            file_name = f"{self.model_name.split(sep='.')[0]}.pdf"
+            file_name = f"{self.model_name.rsplit('.', 1)[0]}.pdf"
             keras.utils.plot_model(self.model, to_file=file_name, show_shapes=True, show_layer_names=True)
diff --git a/src/run_modules/pre_processing.py b/src/run_modules/pre_processing.py
index 3263f5c4562eeac321c7ce621df551fdf6373ba0..1d014c9e6f4fc0a9168c4d3d31b1141c39fff2a1 100644
--- a/src/run_modules/pre_processing.py
+++ b/src/run_modules/pre_processing.py
@@ -137,9 +137,10 @@ class PreProcessing(RunEnvironment):
         for station in all_stations:
             t_inner.run()
             try:
-                # (history, label) = data_gen[station]
                 data = data_gen.get_data_generator(key=station, load_local_tmp_storage=load_tmp,
                                                    save_local_tmp_storage=save_tmp)
+                if data.history is None:
+                    raise AttributeError
                 valid_stations.append(station)
                 logging.debug(f'{station}: history_shape = {data.history.transpose("datetime", "window", "Stations", "variables").shape}')
                 logging.debug(f"{station}: loading time = {t_inner}")
diff --git a/test/test_model_modules/test_linear_model.py b/test/test_model_modules/test_linear_model.py
new file mode 100644
index 0000000000000000000000000000000000000000..e4e10e9db04ba041d61d6ebcf5de3a23380c8ebe
--- /dev/null
+++ b/test/test_model_modules/test_linear_model.py
@@ -0,0 +1,8 @@
+
+from src.model_modules.linear_model import OrdinaryLeastSquaredModel
+
+
+class TestOrdinaryLeastSquareModel:
+
+    def test_constant_input_variable(self):
+        pass