Zend Element File with multifile option

Question

I´m using the Zend_Form_Element_File to upload some files that works just fine, but only if I fill all fields.

$this->addElement( 'file', 'moh_file', array(
        'label'         => 'Datei',
        'destination'   => '/tmp',
        'ValueDisabled' => true,
        'MultiFile'     => 3,
        'validators' => array(
            array('Size', false, 100000000 ),
            array('Extension', false, array( 'mp3', 'wav' ) ),
            array('Count', false, array( 'min' => 0, 'max' => 5 ) ),
            ),
        'class'         => 'long',
        'decorators'    => $file_upload_decorators,
    ));

But if I only want to upload a single file that fails and the adapter only says that: File 'moh_file_1_' was not uploaded

Can anybody tell me what to do ?