diff --git a/openmc/mgxs/library.py b/openmc/mgxs/library.py
index 99da0af55e..2c4423c257 100644
--- a/openmc/mgxs/library.py
+++ b/openmc/mgxs/library.py
@@ -1090,7 +1090,7 @@ class Library:
                                                subdomain=subdomain)
 
         if 'beta' in self.mgxs_types:
-            mymgxs = self.get_mgxs(domain, 'nu-fission')
+            mymgxs = self.get_mgxs(domain, 'beta')
             xsdata.set_beta_mgxs(mymgxs, xs_type=xs_type, nuclide=[nuclide],
                                  subdomain=subdomain)