diff --git a/doc/src/sgml/plpgsql.sgml b/doc/src/sgml/plpgsql.sgml
new file mode 100644
index 5a1e33f..6c203b5
*** a/doc/src/sgml/plpgsql.sgml
--- b/doc/src/sgml/plpgsql.sgml
*************** SELECT merge_db(1, 'dennis');
*** 2561,2567 ****
  
       This coding assumes the <literal>unique_violation</> error is caused by
       the <command>INSERT</>, and not by, say, an <command>INSERT</> in a
!      trigger function on the table.  More safety could be had by using the
       features discussed next to check that the trapped error was the one
       expected.
      </para>
--- 2561,2569 ----
  
       This coding assumes the <literal>unique_violation</> error is caused by
       the <command>INSERT</>, and not by, say, an <command>INSERT</> in a
!      trigger function on the table.  It also assumes that the
!      <literal>unique_violation</> error is caused by the primary key and not
!      another unique constraint.  More safety could be had by using the
       features discussed next to check that the trapped error was the one
       expected.
      </para>