$validationMessages Doesn't work!

Hi.
here is my sample code

PHP Code:

protected $validationRules = [
 
 'rePassword' => ['rules'=>'required|matches[password]','label'=>'Password repeat'],
    ];

protected $validationMessages = [

'rePassword'        => [
                      'required' => 'error'
                ]

]; 


the validation works fine. but error messages shows:

• The Password repeat field is required.
  

How can I use error messages in $validationMessages?