Inserting a new entity with a custom mapping type does not call convertToDatabaseValueSQL() when using InheritanceType("JOINED")

When using class type inheritance - @InheritanceType("JOINED") and inserting new entity with a custom mapping type, custom type method convertToDatabaseValueSQL() is never called.

Here is sample class mapping:

 
/**
 * @Table(name="item")
 * @Entity
 * @InheritanceType("JOINED")
 * @DiscriminatorColumn(name="type_id", type="smallint")
 * @DiscriminatorMap({1 = "ItemPerson"})
 */
class Item {

	/**
	 * @Column(name="tsv", type="tsvector", nullable=true)
	 */
	protected $tsv;
}

/**
 * @Table(name="item_person")
 * @Entity
 */
class ItemPerson extends Item
{
}

I am using the same custom TsvectorType with simple entities and even Mapped Superclasses and it works perfectly, however on InheritanceType("JOINED") method convertToDatabaseValueSQL() is never called :/
Hope someone knows how to fix this.
Thank you.