diff --git a/mlpp_lib/normalizers.py b/mlpp_lib/normalizers.py
index 4b87cb4..d501b3c 100644
--- a/mlpp_lib/normalizers.py
+++ b/mlpp_lib/normalizers.py
@@ -30,8 +30,8 @@ class DataTransformer:
     def __init__(
         self,
         method_vars_dict: Optional[dict[str, list[str]]] = None,
-        default: Optional[str] = "Standardizer",
-        fillvalue: float = -5,
+        default: str = "Standardizer",
+        fillvalue: Optional[float] = -5,
     ):
 
         self.method_vars_dict = method_vars_dict
diff --git a/tests/test_train.py b/tests/test_train.py
index c32b7c9..d6b99f7 100644
--- a/tests/test_train.py
+++ b/tests/test_train.py
@@ -156,7 +156,7 @@ def test_train_fromfile(tmp_path, cfg):
 
     splitter_options = ValidDataSplitterOptions(time="lists", station="lists")
     datasplitter = DataSplitter(splitter_options.time_split, splitter_options.station_split)
-    datanormalizer = DataTransformer(cfg["normalizer"])
+    datanormalizer = DataTransformer(**["normalizer"])
     batch_dims = ["forecast_reference_time", "t", "station"]
     datamodule = DataModule(
         features=cfg["features"],