diff --git a/openmc/mgxs/__init__.py b/openmc/mgxs/__init__.py
index 515a43a7d..86e9dce9e 100644
--- a/openmc/mgxs/__init__.py
+++ b/openmc/mgxs/__init__.py
@@ -1,3 +1,4 @@
+import numpy as np
 
 from openmc.mgxs.groups import EnergyGroups
 from openmc.mgxs.library import Library