diff --git a/src/backend/access/common/heaptuple.c b/src/backend/access/common/heaptuple.c
index 08d2b21c231..034dfe574f1 100644
--- a/src/backend/access/common/heaptuple.c
+++ b/src/backend/access/common/heaptuple.c
@@ -871,7 +871,8 @@ heap_modifytuple(HeapTuple tuple,
  *		the inverse of heap_form_tuple.
  *
  *		Storage for the values/isnull arrays is provided by the caller;
- *		it should be sized according to tupleDesc->natts not tuple->t_natts.
+ *		it should be sized according to tupleDesc->natts not
+ *		HeapTupleHeaderGetNatts(tuple->t_data).
  *
  *		Note that for pass-by-reference datatypes, the pointer placed
  *		in the Datum will point into the given tuple.
@@ -978,7 +979,8 @@ heap_deform_tuple(HeapTuple tuple, TupleDesc tupleDesc,
  *		the inverse of heap_formtuple.
  *
  *		Storage for the values/nulls arrays is provided by the caller;
- *		it should be sized according to tupleDesc->natts not tuple->t_natts.
+ *		it should be sized according to tupleDesc->natts not
+ *		HeapTupleHeaderGetNatts(tuple->t_data).
  *
  *		Note that for pass-by-reference datatypes, the pointer placed
  *		in the Datum will point into the given tuple.