src/User/Form/UserAdd.php
public function isValid()
    {
    	$data = $this->data;
    	
        if(((isset($data['password']) && $data['password']) || 
        	(isset($data['repassword']) && $data['repassword'])) && !$this->skipCurrentPasswordValidation) {
        	$filter = $this->getInputFilter();
        	$cp = $filter->get('currentpassword');
        	$cp->setRequired(true);
        	$cp->setAllowEmpty(false);
        }
        
    	return parent::isValid();
    }
public function isValid()
    {
    	$data = $this->data;
    	
        if(((isset($data['password']) && $data['password']) || 
        	(isset($data['repassword']) && $data['repassword'])) && !$this->skipCurrentPasswordValidation) {
        	$filter = $this->getInputFilter();
        	$cp = $filter->get('currentpassword');
        	$cp->setRequired(true);
        	$cp->setAllowEmpty(false);
        }
        
    	return parent::isValid();
    }
(non-PHPdoc)
@see \Zend\Form\Form::isValid()