diff --git a/doc/src/sgml/ref/alter_table.sgml b/doc/src/sgml/ref/alter_table.sgml
index 39927be41e..f23e704b8c 100644
--- a/doc/src/sgml/ref/alter_table.sgml
+++ b/doc/src/sgml/ref/alter_table.sgml
@@ -522,6 +522,9 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
       (See <xref linkend="sql-altertable-notes"/> 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>