diff --git a/src/hb-subset-private.hh b/src/hb-subset-private.hh
index eb4147dce..31fceb470 100644
--- a/src/hb-subset-private.hh
+++ b/src/hb-subset-private.hh
@@ -45,6 +45,7 @@ struct hb_subset_input_t {
 
 struct hb_subset_face_t {
   hb_object_header_t header;
+  ASSERT_POD ();
 
   hb_face_t *face;
   OT::cmap::accelerator_t cmap;