diff --git a/smol/cofe/expansion.py b/smol/cofe/expansion.py
index 9dd58b279..4be6b702e 100644
--- a/smol/cofe/expansion.py
+++ b/smol/cofe/expansion.py
@@ -179,7 +179,7 @@ def eci(self):
         num_ext_terms = len(self._subspace.external_terms)  # check for extra terms
         coefs = self.coefs[:-num_ext_terms] if num_ext_terms else self.coefs[:]
         eci = coefs.copy()
-        eci /= self._subspace.function_total_multiplicities
+        eci = eci / self._subspace.function_total_multiplicities
         return eci
 
     @cached_property
diff --git a/smol/cofe/wrangling/wrangler.py b/smol/cofe/wrangling/wrangler.py
index 482b7c53b..10f6251a4 100644
--- a/smol/cofe/wrangling/wrangler.py
+++ b/smol/cofe/wrangling/wrangler.py
@@ -426,7 +426,7 @@ def get_property_vector(self, key, normalize=True):
                 ) from error
 
         if normalize:
-            properties /= self.sizes
+            properties = properties / self.sizes
 
         return properties
 
diff --git a/tests/test_utils/test_cluster_utils.py b/tests/test_utils/test_cluster_utils.py
index 559c87d3c..e2865504b 100644
--- a/tests/test_utils/test_cluster_utils.py
+++ b/tests/test_utils/test_cluster_utils.py
@@ -1,3 +1,4 @@
+import numpy as np
 import pytest
 
 from smol.utils.cluster.container import (
@@ -13,15 +14,18 @@
     "IntArrayContainer, dim", [(IntArray1DContainer, 1), (IntArray2DContainer, 2)]
 )
 def test_int_container(IntArrayContainer, dim, rng):
+    # Use np.int_ to ensure cross-platform compatibility.
     arrays = tuple(
-        rng.integers(1, 5, size=dim * (rng.integers(1, 5),)) for _ in range(10)
+        rng.integers(1, 5, size=dim * (rng.integers(1, 5),)).astype(np.int_)
+        for _ in range(10)
     )
     container = IntArrayContainer(arrays)
     assert len(container) == 10
 
     # test setting the same sized list (no memory reallocation)
     new_arrays = tuple(
-        rng.integers(1, 5, size=dim * (rng.integers(1, 5),)) for _ in range(10)
+        rng.integers(1, 5, size=dim * (rng.integers(1, 5),)).astype(np.int_)
+        for _ in range(10)
     )
     container.set_arrays(new_arrays)
 
@@ -29,7 +33,8 @@ def test_int_container(IntArrayContainer, dim, rng):
 
     # test setting a different sized list (needs memory reallocation)
     new_arrays = tuple(
-        rng.integers(1, 5, size=dim * (rng.integers(1, 5),)) for _ in range(12)
+        rng.integers(1, 5, size=dim * (rng.integers(1, 5),)).astype(np.int_)
+        for _ in range(12)
     )
     container.set_arrays(new_arrays)
 
@@ -37,7 +42,7 @@ def test_int_container(IntArrayContainer, dim, rng):
 
     with pytest.raises(ValueError):
         new_arrays = tuple(
-            rng.integers(1, 5, size=(dim + 1) * (rng.integers(1, 5),))
+            rng.integers(1, 5, size=(dim + 1) * (rng.integers(1, 5),)).astype(np.int_)
             for _ in range(12)
         )
         container.set_arrays(new_arrays)
@@ -79,7 +84,9 @@ def test_orbit_container(rng):
         orbit_id = i
         bit_id = rng.integers(1, 5, dtype=int)
         correlation_tensors = rng.random(tuple(rng.integers(1, 5, size=2)))
-        tensor_indices = rng.integers(1, 5, size=correlation_tensors.shape[0])
+        tensor_indices = rng.integers(1, 5, size=correlation_tensors.shape[0]).astype(
+            np.int_
+        )
         orbit_data.append((orbit_id, bit_id, correlation_tensors, tensor_indices))
 
     container = OrbitContainer(tuple(orbit_data))
@@ -91,7 +98,9 @@ def test_orbit_container(rng):
         orbit_id = i
         bit_id = rng.integers(1, 5, dtype=int)
         correlation_tensors = rng.random(tuple(rng.integers(1, 5, size=2)))
-        tensor_indices = rng.integers(1, 5, size=correlation_tensors.shape[0])
+        tensor_indices = rng.integers(1, 5, size=correlation_tensors.shape[0]).astype(
+            np.int_
+        )
         new_orbit_data.append((orbit_id, bit_id, correlation_tensors, tensor_indices))
 
     container.set_orbits(tuple(new_orbit_data))
@@ -103,7 +112,9 @@ def test_orbit_container(rng):
         orbit_id = i
         bit_id = rng.integers(1, 5, dtype=int)
         correlation_tensors = rng.random(tuple(rng.integers(1, 5, size=2)))
-        tensor_indices = rng.integers(1, 5, size=correlation_tensors.shape[0])
+        tensor_indices = rng.integers(1, 5, size=correlation_tensors.shape[0]).astype(
+            np.int_
+        )
         new_orbit_data.append((orbit_id, bit_id, correlation_tensors, tensor_indices))
 
     container.set_orbits(tuple(new_orbit_data))