diff --git a/tests/unit_tests/test_filters.py b/tests/unit_tests/test_filters.py
index ec051d9fd0..4e741e60f9 100644
--- a/tests/unit_tests/test_filters.py
+++ b/tests/unit_tests/test_filters.py
@@ -252,6 +252,6 @@ def test_energy():
 def test_lethargy_bin_width():
     f = openmc.EnergyFilter.from_group_structure('VITAMIN-J-175')
     assert len(f.lethargy_bin_width) == 175
-    energy_bins = openmc.mgxs.GROUP_STRUCTURES['VITAMIN-J-175'] 
-    assert f.lethargy_bin_width[0] == math.log10(energy_bins[1]/energy_bins[0])
-    assert f.lethargy_bin_width[-1] == math.log10(energy_bins[-1]/energy_bins[-2])
+    energy_bins = openmc.mgxs.GROUP_STRUCTURES['VITAMIN-J-175']
+    assert f.lethargy_bin_width[0] == np.log10(energy_bins[1]/energy_bins[0])
+    assert f.lethargy_bin_width[-1] == np.log10(energy_bins[-1]/energy_bins[-2])