diff --git a/src/backend/access/nbtree/nbtinsert.c b/src/backend/access/nbtree/nbtinsert.c
index d64cbd9822..ecee5ac7f6 100644
--- a/src/backend/access/nbtree/nbtinsert.c
+++ b/src/backend/access/nbtree/nbtinsert.c
@@ -1299,7 +1299,7 @@ _bt_split(Relation rel, Buffer buf, Buffer cbuf, OffsetNumber firstright,
 
 			lastrdata->data = (char *) newitem;
 			lastrdata->len = MAXALIGN(newitemsz);
-			lastrdata->buffer = buf;	/* backup block 1 */
+			lastrdata->buffer = buf;	/* backup block 0 */
 			lastrdata->buffer_std = true;
 		}
 
@@ -1320,7 +1320,7 @@ _bt_split(Relation rel, Buffer buf, Buffer cbuf, OffsetNumber firstright,
 			item = (IndexTuple) PageGetItem(origpage, itemid);
 			lastrdata->data = (char *) item;
 			lastrdata->len = MAXALIGN(IndexTupleSize(item));
-			lastrdata->buffer = buf;	/* backup block 1 */
+			lastrdata->buffer = buf;	/* backup block 0 */
 			lastrdata->buffer_std = true;
 		}
 
@@ -1333,11 +1333,11 @@ _bt_split(Relation rel, Buffer buf, Buffer cbuf, OffsetNumber firstright,
 			 * Although we don't need to WAL-log anything on the left page, we
 			 * still need XLogInsert to consider storing a full-page image of
 			 * the left page, so make an empty entry referencing that buffer.
-			 * This also ensures that the left page is always backup block 1.
+			 * This also ensures that the left page is always backup block 0.
 			 */
 			lastrdata->data = NULL;
 			lastrdata->len = 0;
-			lastrdata->buffer = buf;	/* backup block 1 */
+			lastrdata->buffer = buf;	/* backup block 0 */
 			lastrdata->buffer_std = true;
 		}
 
@@ -1353,7 +1353,7 @@ _bt_split(Relation rel, Buffer buf, Buffer cbuf, OffsetNumber firstright,
 			cblkno = BufferGetBlockNumber(cbuf);
 			lastrdata->data = (char *) &cblkno;
 			lastrdata->len = sizeof(BlockNumber);
-			lastrdata->buffer = cbuf;	/* backup block 2 */
+			lastrdata->buffer = cbuf;	/* backup block 1 */
 			lastrdata->buffer_std = true;
 		}
 
@@ -1386,7 +1386,7 @@ _bt_split(Relation rel, Buffer buf, Buffer cbuf, OffsetNumber firstright,
 
 			lastrdata->data = NULL;
 			lastrdata->len = 0;
-			lastrdata->buffer = sbuf;	/* bkp block 2 (leaf) or 3 (non-leaf) */
+			lastrdata->buffer = sbuf;	/* bkp block 1 (leaf) or 2 (non-leaf) */
 			lastrdata->buffer_std = true;
 		}
 
diff --git a/src/backend/access/nbtree/nbtxlog.c b/src/backend/access/nbtree/nbtxlog.c
index 640639c175..5f9fc49e78 100644
--- a/src/backend/access/nbtree/nbtxlog.c
+++ b/src/backend/access/nbtree/nbtxlog.c
@@ -300,8 +300,8 @@ btree_xlog_split(bool onleft, bool isroot,
 	 */
 	if (!isleaf)
 	{
-		if (record->xl_info & XLR_BKP_BLOCK(2))
-			(void) RestoreBackupBlock(lsn, record, 2, false, false);
+		if (record->xl_info & XLR_BKP_BLOCK(1))
+			(void) RestoreBackupBlock(lsn, record, 1, false, false);
 		else
 			_bt_clear_incomplete_split(lsn, record, xlrec->node, cblkno);
 	}
@@ -439,10 +439,10 @@ btree_xlog_split(bool onleft, bool isroot,
 	if (xlrec->rnext != P_NONE)
 	{
 		/*
-		 * the backup block containing right sibling is 2 or 3, depending
+		 * the backup block containing right sibling is 1 or 2, depending
 		 * whether this was a leaf or internal page.
 		 */
-		int			rnext_index = isleaf ? 2 : 3;
+		int			rnext_index = isleaf ? 1 : 2;
 
 		if (record->xl_info & XLR_BKP_BLOCK(rnext_index))
 			(void) RestoreBackupBlock(lsn, record, rnext_index, false, false);