diff --git a/doc/src/sgml/ref/pg_basebackup.sgml b/doc/src/sgml/ref/pg_basebackup.sgml
index a3e292d44a..35d7fb605f 100644
--- a/doc/src/sgml/ref/pg_basebackup.sgml
+++ b/doc/src/sgml/ref/pg_basebackup.sgml
@@ -83,8 +83,13 @@ PostgreSQL documentation
     </listitem>
     <listitem>
      <para>
-      If you are using <literal>-X none</literal>, there is no guarantee that all
-      WAL files required for the backup are archived at the end of backup.
+       If you are using <literal>-X none</literal>, there is no guarantee on
+       the primary that all WAL files required for the backup are archived at
+       the end of backup. When the standby is configured as
+       archive_mode=always, pg_basebackup may wait for a long time for all the
+       required WAL files to be archived.  In that case, You may need to
+       call <function>pg_switch_wal()</function> on the primary to complete it
+       sooner.
      </para>
     </listitem>
     <listitem>