diff --git a/doc/src/sgml/ref/alter_table.sgml b/doc/src/sgml/ref/alter_table.sgml
index de80a1901b5..ea27df25698 100644
--- a/doc/src/sgml/ref/alter_table.sgml
+++ b/doc/src/sgml/ref/alter_table.sgml
@@ -485,6 +485,9 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
       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>