diff --git a/src/anemoi/models/preprocessing/normalizer.py b/src/anemoi/models/preprocessing/normalizer.py
index 07dfdfc..73f9ec3 100644
--- a/src/anemoi/models/preprocessing/normalizer.py
+++ b/src/anemoi/models/preprocessing/normalizer.py
@@ -11,7 +11,7 @@
 import warnings
 from typing import Optional
 
-from anemoi.datasets.data.observations import ListOfArray
+from anemoi.datasets.data.observations import AnemoiState
 
 import numpy as np
 import torch
@@ -53,10 +53,10 @@ def __init__(
         mean = statistics["mean"]
         stdev = statistics["stdev"]
         
-        mean = ListOfArray(mean)
-        stdev = ListOfArray(stdev)
-        minimum = ListOfArray(minimum)
-        maximum = ListOfArray(maximum)
+        mean = AnemoiState(mean)
+        stdev = AnemoiState(stdev)
+        minimum = AnemoiState(minimum)
+        maximum = AnemoiState(maximum)
 
         self._validate_normalization_inputs(name_to_index_training_input, minimum, maximum, mean, stdev)