diff --git a/src/hb-ot-layout-private.hh b/src/hb-ot-layout-private.hh
index 27648c909..93d2d7601 100644
--- a/src/hb-ot-layout-private.hh
+++ b/src/hb-ot-layout-private.hh
@@ -370,6 +370,12 @@ _hb_glyph_info_is_mark (const hb_glyph_info_t *info)
   return !!(info->glyph_props() & HB_OT_LAYOUT_GLYPH_PROPS_MARK);
 }
 
+static inline bool
+_hb_glyph_info_substituted (const hb_glyph_info_t *info)
+{
+  return !!(info->glyph_props() & HB_OT_LAYOUT_GLYPH_PROPS_SUBSTITUTED);
+}
+
 static inline bool
 _hb_glyph_info_ligated (const hb_glyph_info_t *info)
 {