diff --git a/src/hb-open-type-private.hh b/src/hb-open-type-private.hh
index 78208a2427f0cd79b162eac30120c51d582afd4c..d1bcf8ea1e8fbaefe44d193bd67088a75e76cc3d 100644
--- a/src/hb-open-type-private.hh
+++ b/src/hb-open-type-private.hh
@@ -285,6 +285,7 @@ struct Sanitizer
 
     _hb_sanitize_init (&context, blob);
 
+    /* We drop const here */
     Type *t = &CAST (Type, * (char *) CharP(context.start), 0);
 
     sane = t->sanitize (SANITIZE_ARG_INIT);