Doctrine_Validator throws validation exception for field 'owner_type' in class 'Image' being null when trying to save a new record with the subclass Brand_Image in following setup: (I've removed unrelated fields/relations/indexes of class definitions to simplify)

Class definitions:

class Image extends Doctrine_Record
{
    public function setTableDefinition() {
        $this->hasColumn('id', 'integer', null, array('primary' => true, 'sequence' => true));
        $this->hasColumn('owner_id', 'integer', null, array('notnull' => true));
        $this->hasColumn('owner_type', 'integer', 5, array('notnull' => true));
        $this->hasColumn('name', 'string', 128, array('notnull' => true, 'unique' => true));

        $this->setSubclasses(array(
            'Manufacturer_Image'    => array('owner_type' => 1),
            'Brand_Image'           => array('owner_type' => 2),
            'Category_Image'        => array('owner_type' => 3),
            'Family_Image'          => array('owner_type' => 4),
            'Product_Image'         => array('owner_type' => 5),
            'Productversion_Image'  => array('owner_type' => 6)
        ));
    }
}

class Brand_Image extends Image
{
}

class Brand extends Doctrine_Record
{
    public function setTableDefinition() {
        $this->hasColumn('id', 'integer', null, array('primary' => true, 'sequence' => true));
        $this->hasColumn('name', 'string', 255, array('notnull' => true));
    }
    
    public function setUp() {
        $this->hasMany(
            'Brand_Image',
            array(
                'local' => 'id',
                'foreign' => 'owner_id'
            )
        );
    }
}

Use case resulting exception:

$brand = new Brand;
$brand->name = 'The Great Brand';
$brand->Brand_Image[0]->name = 'imagename';
$brand->save();

But actually owner_type is not null altough it's not set by user as Doctrine sets the value automatically as defined in subclasses-definition.