diff --git a/src/hb-serialize.hh b/src/hb-serialize.hh
index a4303fc34..87aafe0e2 100644
--- a/src/hb-serialize.hh
+++ b/src/hb-serialize.hh
@@ -133,9 +133,9 @@ struct hb_serialize_context_t
 
   bool successful () const { return !bool (errors); }
 
-  bool ran_out_of_room () const { return errors & HB_SERIALIZE_ERROR_OUT_OF_ROOM; }
-  bool offset_overflow () const { return errors & HB_SERIALIZE_ERROR_OFFSET_OVERFLOW; }
-  bool only_offset_overflow () const { return errors == HB_SERIALIZE_ERROR_OFFSET_OVERFLOW; }
+  HB_NODISCARD bool ran_out_of_room () const { return errors & HB_SERIALIZE_ERROR_OUT_OF_ROOM; }
+  HB_NODISCARD bool offset_overflow () const { return errors & HB_SERIALIZE_ERROR_OFFSET_OVERFLOW; }
+  HB_NODISCARD bool only_offset_overflow () const { return errors == HB_SERIALIZE_ERROR_OFFSET_OVERFLOW; }
 
   void reset (void *start_, unsigned int size)
   {