diff --git a/README.md b/README.md
index 5348a7b..f499f22 100644
--- a/README.md
+++ b/README.md
@@ -1,8 +1,11 @@
-[![GitHub license](https://img.shields.io/github/license/fawno/AEAT.svg)](https://github.com/fawno/AEAT/blob/master/LICENSE)
-[![GitHub release](https://img.shields.io/github/release/fawno/AEAT.svg)](https://github.com/fawno/AEAT/releases)
-[![Packagist](https://img.shields.io/packagist/v/fawno/AEAT.svg)](https://packagist.org/packages/fawno/aeat)
+[![GitHub license](https://img.shields.io/github/license/fawno/AEAT)](https://github.com/fawno/AEAT/blob/master/LICENSE)
+[![GitHub release](https://img.shields.io/github/release/fawno/AEAT)](https://github.com/fawno/AEAT/releases)
+[![Packagist](https://img.shields.io/packagist/v/fawno/AEAT)](https://packagist.org/packages/fawno/aeat)
 [![Packagist Downloads](https://img.shields.io/packagist/dt/fawno/AEAT)](https://packagist.org/packages/fawno/aeat/stats)
-[![Documentation](https://img.shields.io/badge/manual-wsdlVNif-blue.svg)](docs/wsdlVNif.md)
+[![GitHub issues](https://img.shields.io/github/issues/fawno/AEAT)](https://github.com/fawno/AEAT/issues)
+[![GitHub forks](https://img.shields.io/github/forks/fawno/AEAT)](https://github.com/fawno/AEAT/network)
+[![GitHub stars](https://img.shields.io/github/stars/fawno/AEAT)](https://github.com/fawno/AEAT/stargazers)
+[![Documentation](https://img.shields.io/badge/manual-wsdlVNif-blue)](docs/wsdlVNif.md)
 
 # AEAT
 Clases para los servicios web de la [AEAT](http://www.agenciatributaria.es/)
diff --git a/composer.json b/composer.json
index 54dcf4d..a453dc5 100644
--- a/composer.json
+++ b/composer.json
@@ -1,6 +1,6 @@
 {
   "name": "fawno/aeat",
-  "version": "1.0.2",
+  "version": "1.0.3",
   "description": "Clases para los servicios web de la AEAT",
   "license": "MIT",
   "authors": [
diff --git a/src/wsdlVNif.php b/src/wsdlVNif.php
index d92d55b..ce54fc5 100644
--- a/src/wsdlVNif.php
+++ b/src/wsdlVNif.php
@@ -30,7 +30,7 @@ public function __construct ($local_cert, $passphrase, $options = [], $ssl_verif
     protected function stream_context ($ssl_verifypeer = true, $options = []) {
       $options['http']['user_agent'] = 'PHPSoapClient';
       $options['ssl']['ciphers'] = 'DEFAULT@SECLEVEL=1';
-      
+
       if (!$ssl_verifypeer) {
         $options['ssl']['verify_peer'] = false;
         $options['ssl']['verify_peer_name'] = false;
@@ -51,8 +51,8 @@ public function VNif ($contribuyentes) {
     public function VNifV2 ($contribuyentes) {
       return $this->__soapCall('VNifV2', [['Contribuyente' => $contribuyentes]]);
     }
-  
-    public function nif_validation ($nif) {
+
+    public static function nif_validation ($nif) {
       if (preg_match('~(ES)?([\w\d]{9})~', strtoupper($nif), $parts)) {
         $nif = end($parts);
         if (preg_match('~(^[XYZ\d]\d{7})([TRWAGMYFPDXBNJZSQVHLCKE]$)~', $nif, $parts)) {