diff --git a/src/backend/access/nbtree/nbtinsert.c b/src/backend/access/nbtree/nbtinsert.c
index 1675298f73..cbd4ec3b39 100644
--- a/src/backend/access/nbtree/nbtinsert.c
+++ b/src/backend/access/nbtree/nbtinsert.c
@@ -2413,7 +2413,7 @@ _bt_newroot(Relation rel, Buffer lbuf, Buffer rbuf)
 	left_item = (IndexTuple) palloc(left_item_sz);
 	left_item->t_info = left_item_sz;
 	BTreeTupleSetDownLink(left_item, lbkno);
-	BTreeTupleSetNAtts(left_item, 0);
+	BTreeTupleSetNAtts(left_item, 0, false);
 
 	/*
 	 * Create downlink item for right page.  The key for it is obtained from
@@ -2571,7 +2571,7 @@ _bt_pgaddtup(Page page,
 	{
 		trunctuple = *itup;
 		trunctuple.t_info = sizeof(IndexTupleData);
-		BTreeTupleSetNAtts(&trunctuple, 0);
+		BTreeTupleSetNAtts(&trunctuple, 0, false);
 		itup = &trunctuple;
 		itemsize = sizeof(IndexTupleData);
 	}
diff --git a/src/backend/access/nbtree/nbtsort.c b/src/backend/access/nbtree/nbtsort.c
index 29a6f5ade6..9d249f7a6b 100644
--- a/src/backend/access/nbtree/nbtsort.c
+++ b/src/backend/access/nbtree/nbtsort.c
@@ -771,7 +771,7 @@ _bt_sortaddtup(Page page,
 	{
 		trunctuple = *itup;
 		trunctuple.t_info = sizeof(IndexTupleData);
-		BTreeTupleSetNAtts(&trunctuple, 0);
+		BTreeTupleSetNAtts(&trunctuple, 0, false);
 		itup = &trunctuple;
 		itemsize = sizeof(IndexTupleData);
 	}
@@ -1045,7 +1045,7 @@ _bt_buildadd(BTWriteState *wstate, BTPageState *state, IndexTuple itup,
 		Assert(state->btps_lowkey == NULL);
 		state->btps_lowkey = palloc0(sizeof(IndexTupleData));
 		state->btps_lowkey->t_info = sizeof(IndexTupleData);
-		BTreeTupleSetNAtts(state->btps_lowkey, 0);
+		BTreeTupleSetNAtts(state->btps_lowkey, 0, false);
 	}
 
 	/*
diff --git a/src/backend/access/nbtree/nbtutils.c b/src/backend/access/nbtree/nbtutils.c
index 86cec24859..08d7201f19 100644
--- a/src/backend/access/nbtree/nbtutils.c
+++ b/src/backend/access/nbtree/nbtutils.c
@@ -2239,7 +2239,7 @@ _bt_truncate(Relation rel, IndexTuple lastleft, IndexTuple firstright,
 	 */
 	if (keepnatts <= nkeyatts)
 	{
-		BTreeTupleSetNAtts(pivot, keepnatts);
+		BTreeTupleSetNAtts(pivot, keepnatts, false);
 		return pivot;
 	}
 
@@ -2262,11 +2262,13 @@ _bt_truncate(Relation rel, IndexTuple lastleft, IndexTuple firstright,
 	/* Cannot leak memory here */
 	pfree(pivot);
 
-	/* Store heap TID in enlarged pivot tuple */
+	/*
+	 * Store all of firstright's key attribute values plus a tiebreaker heap
+	 * TID value in enlarged pivot tuple
+	 */
 	tidpivot->t_info &= ~INDEX_SIZE_MASK;
 	tidpivot->t_info |= newsize;
-	BTreeTupleSetNAtts(tidpivot, nkeyatts);
-	BTreeTupleSetAltHeapTID(tidpivot);
+	BTreeTupleSetNAtts(tidpivot, nkeyatts, true);
 	pivotheaptid = BTreeTupleGetHeapTID(tidpivot);
 
 	/*
diff --git a/src/include/access/nbtree.h b/src/include/access/nbtree.h
index 5f67fc04e0..072a41ef8b 100644
--- a/src/include/access/nbtree.h
+++ b/src/include/access/nbtree.h
@@ -460,34 +460,30 @@ BTreeTupleSetDownLink(IndexTuple pivot, BlockNumber blkno)
 	)
 
 /*
- * Set number of attributes in tuple, making it into a pivot tuple
+ * Set number of key attributes in tuple.
+ *
+ * The heap TID tiebreaker attribute bit may also be set here, indicating that
+ * a heap TID value will be stored at the end of the tuple (i.e. using the
+ * special pivot tuple representation).
  */
 static inline void
-BTreeTupleSetNAtts(IndexTuple itup, int natts)
+BTreeTupleSetNAtts(IndexTuple itup, uint16 nkeyatts, bool heaptid)
 {
-	Assert(natts <= INDEX_MAX_KEYS);
+	Assert(nkeyatts <= INDEX_MAX_KEYS);
+	Assert((nkeyatts & BT_RESERVED_OFFSET_MASK) == 0);
+	Assert(!heaptid || nkeyatts > 0);
+	Assert(!BTreeTupleIsPivot(itup) || nkeyatts == 0);
 
 	itup->t_info |= INDEX_ALT_TID_MASK;
-	/* BT_IS_POSTING bit may be unset -- tuple always becomes a pivot tuple */
-	ItemPointerSetOffsetNumber(&itup->t_tid, natts);
+
+	if (heaptid)
+		nkeyatts |= BT_PIVOT_HEAP_TID_ATTR;
+
+	/* BT_IS_POSTING bit is deliberately unset here */
+	ItemPointerSetOffsetNumber(&itup->t_tid, nkeyatts);
 	Assert(BTreeTupleIsPivot(itup));
 }
 
-/*
- * Set the bit indicating heap TID attribute present in pivot tuple
- */
-static inline void
-BTreeTupleSetAltHeapTID(IndexTuple pivot)
-{
-	OffsetNumber existing;
-
-	Assert(BTreeTupleIsPivot(pivot));
-
-	existing = ItemPointerGetOffsetNumberNoCheck(&pivot->t_tid);
-	ItemPointerSetOffsetNumber(&pivot->t_tid,
-							   existing | BT_PIVOT_HEAP_TID_ATTR);
-}
-
 /*
  * Get/set leaf page's "top parent" link from its high key.  Used during page
  * deletion.
@@ -505,7 +501,7 @@ static inline void
 BTreeTupleSetTopParent(IndexTuple leafhikey, BlockNumber blkno)
 {
 	ItemPointerSetBlockNumber(&leafhikey->t_tid, blkno);
-	BTreeTupleSetNAtts(leafhikey, 0);
+	BTreeTupleSetNAtts(leafhikey, 0, false);
 }
 
 /*