diff --git a/pyrolite/geochem/ind.py b/pyrolite/geochem/ind.py
index 5090b541..dd2783c5 100644
--- a/pyrolite/geochem/ind.py
+++ b/pyrolite/geochem/ind.py
@@ -429,7 +429,7 @@ def get_ionic_radii(
 
     Returns
     --------
-    :class:`pandas.Series` | :class:`float`
+    :class:`pandas.Series` | :class:`numpy.ndarray` | :class:`float`
         Series with viable ion charge and coordination, with associated radii in
         angstroms. If the ion charge and coordiation are completely specified and
         found in the table, a single value will be returned instead.
diff --git a/test/geochem/geochem_ind.py b/test/geochem/geochem_ind.py
index 87929848..714bdfa5 100644
--- a/test/geochem/geochem_ind.py
+++ b/test/geochem/geochem_ind.py
@@ -1,5 +1,6 @@
 import unittest
 
+import numpy as np
 import periodictable as pt
 
 from pyrolite.geochem.ind import (
@@ -258,11 +259,11 @@ def test_ree_radii(self):
 
     def test_ree_radii_list(self):
         radii = get_ionic_radii(self.ree, charge=3, coordination=8)
-        self.assertTrue(isinstance(radii, list))
+        self.assertTrue(isinstance(radii, np.ndarray))
 
     def test_ree_radii_list_whittaker_muntus(self):
         radii = get_ionic_radii(self.ree, charge=3, coordination=8, source="whittaker")
-        self.assertTrue(isinstance(radii, list))
+        self.assertTrue(isinstance(radii, np.ndarray))
 
 
 class TestByIncompatibility(unittest.TestCase):