diff --git a/doc/src/sgml/ref/alter_table.sgml b/doc/src/sgml/ref/alter_table.sgml
index 9b2e4c5749..ab5e6bf3d4 100644
--- a/doc/src/sgml/ref/alter_table.sgml
+++ b/doc/src/sgml/ref/alter_table.sgml
@@ -476,6 +476,9 @@ 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>