diff --git a/doc/src/sgml/pgupgrade.sgml b/doc/src/sgml/pgupgrade.sgml
new file mode 100644
index e1cd260..07cb1f9
*** a/doc/src/sgml/pgupgrade.sgml
--- b/doc/src/sgml/pgupgrade.sgml
*************** psql --username postgres --file script.s
*** 553,559 ****
     is to upgrade the primary and use <command>rsync</> to rebuild the
     standbys.  You can run <command>rsync</> while the primary is down,
     or as part of a base backup (<xref linkend="backup-base-backup">)
!    which overwrites the old standby cluster.
    </para>
  
    <para>
--- 553,565 ----
     is to upgrade the primary and use <command>rsync</> to rebuild the
     standbys.  You can run <command>rsync</> while the primary is down,
     or as part of a base backup (<xref linkend="backup-base-backup">)
!    which overwrites the old standby cluster.  Hint bit differences
!    between the primary and standby can cause <command>rsync</> to copy
!    additional data &mdash;  these differences can be reduced by using
!    a fresh standby and by enabling <xref linkend="guc-wal-log-hints">.
!    (While <varname>wal_log_hints</> transfers hint bits from the primary
!    to standbys, additional hint bits are still set on the standbys by
!    read-only queries.)
    </para>
  
    <para>