Add <index> to the <id> node to define the PK index name

Add <index> to the <id> node, I need it to define the name of the PK index.
Using the column index:
<id name="Id">
<column name="Id" index="PK_HelpPage_Id" />
<generator class="hilo" />
</id>

makes SchemaExport to generate 2 indexes (one clustered for the PK, and another non-clustered with the name PK_HelpPage_Id)