diff --git a/openmc/mgxs_library.py b/openmc/mgxs_library.py
index b98902030..34c36ec17 100644
--- a/openmc/mgxs_library.py
+++ b/openmc/mgxs_library.py
@@ -1638,9 +1638,9 @@ class XSdata(object):
                                    xs_type=xs_type, moment=0,
                                    subdomains=subdomain)
             if scatter.scatter_format == 'histogram':
-                scatt = np.sum(scatt, axis=0)
+                scatt = np.sum(scatt, axis=2)
             if nuscatter.scatter_format == 'histogram':
-                nuscatt = np.sum(nuscatt, axis=0)
+                nuscatt = np.sum(nuscatt, axis=2)
             self._multiplicity_matrix[i] = np.divide(nuscatt, scatt)
 
         self._multiplicity_matrix[i] = \