diff --git a/doc/src/sgml/ref/alter_table.sgml b/doc/src/sgml/ref/alter_table.sgml
index 56e134d82a5..f509a35367c 100644
--- a/doc/src/sgml/ref/alter_table.sgml
+++ b/doc/src/sgml/ref/alter_table.sgml
@@ -369,6 +369,9 @@ ALTER TABLE ALL IN TABLESPACE <replaceable class="PARAMETER">name</replaceable>
       endterm="sql-altertable-notes-title"> below for an explanation of the
       usefulness of this command.)
      </para>
+     <para>
+      This command acquires a <literal>SHARE UPDATE EXCLUSIVE</literal> lock.
+     </para>
     </listitem>
    </varlistentry>