diff --git a/dianna/utils/misc.py b/dianna/utils/misc.py
index 944517d5..a2933dfe 100644
--- a/dianna/utils/misc.py
+++ b/dianna/utils/misc.py
@@ -1,6 +1,8 @@
 import inspect
 import warnings
 from pathlib import Path
+import numpy as np
+import numpy.typing
 
 
 def get_function(model_or_function, preprocess_function=None):
@@ -49,7 +51,7 @@ def get_kwargs_applicable_to_function(function, kwargs):
     }
 
 
-def to_xarray(data, axis_labels, required_labels=None):
+def to_xarray(data: numpy.typing.ArrayLike, axis_labels, required_labels=None):
     """Converts numpy data and axes labels to an xarray object."""
     if isinstance(axis_labels, dict):
         # key = axis index, value = label
@@ -59,10 +61,10 @@ def to_xarray(data, axis_labels, required_labels=None):
         indices = list(axis_labels.keys())
         for index in indices:
             if index < 0:
-                axis_labels[data.ndim + index] = axis_labels.pop(index)
+                axis_labels[np.ndim(data) + index] = axis_labels.pop(index)
         labels = [
             axis_labels[index] if index in axis_labels else f'dim_{index}'
-            for index in range(data.ndim)
+            for index in range(np.ndim(data))
         ]
     else:
         labels = list(axis_labels)
diff --git a/setup.cfg b/setup.cfg
index a063f34e..97d15c0b 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -39,7 +39,7 @@ install_requires =
     ipython
     lime
     matplotlib
-    numpy
+    numpy>=1.20
     onnx==1.14.1
     onnx_tf
     onnxruntime