diff --git a/openmc/lib/core.py b/openmc/lib/core.py
index 7be94e03d3..6d9a680e35 100644
--- a/openmc/lib/core.py
+++ b/openmc/lib/core.py
@@ -17,6 +17,7 @@ class _Bank(Structure):
                 ('E', c_double),
                 ('wgt', c_double),
                 ('delayed_group', c_int),
+                ('surf_id', c_int),
                 ('particle', c_int),
                 ('parent_id', c_int64),
                 ('progeny_id', c_int64)]