diff --git a/README.md b/README.md
index 5e138de7..a3f5c458 100755
--- a/README.md
+++ b/README.md
@@ -13,7 +13,7 @@ The SDK supports PHP 5.6 or major
 #### Using Composer
 
 1. Download [Composer](https://getcomposer.org/doc/00-intro.md#installation-linux-unix-macos) if not already installed
-2. Go to your project directory and run `composer require "mercadopago/dx-php:1.12.5"` on the command line.
+2. Go to your project directory and run `composer require "mercadopago/dx-php:1.12.6"` on the command line.
 3. This how your directory structure would look like.
 4. Thats all, you have Mercado Pago SDK installed.
 
diff --git a/composer.json b/composer.json
index 0efda850..c3709eb7 100755
--- a/composer.json
+++ b/composer.json
@@ -3,7 +3,7 @@
   "type": "library",
   "homepage": "https://github.com/mercadopago/sdk-php",
   "license": "MIT",
-  "version": "1.12.5",
+  "version": "1.12.6",
   "config": {
     "platform": {
         "php": "5.6"
diff --git a/src/MercadoPago/Manager.php b/src/MercadoPago/Manager.php
index f4146e15..1eb2a532 100755
--- a/src/MercadoPago/Manager.php
+++ b/src/MercadoPago/Manager.php
@@ -84,9 +84,9 @@ public function execute($entity, $method = 'get', $options = [])
 
         $this->_setDefaultHeaders($configuration->query);
         $this->_setCustomHeaders($entity, $configuration->query);
-        //$this->_setIdempotencyHeader($configuration->query, $configuration, $method);
+        $this->_setIdempotencyHeader($configuration->query, $method);
         $this->setQueryParams($entity);
-        
+
         return $this->_client->{$method}($configuration->url, $configuration->query);
     }
 
@@ -409,32 +409,41 @@ protected function _setDefaultHeaders(&$query)
      * @param        $configuration
      * @param string $method
      */
-    protected function _setIdempotencyHeader(&$query, $configuration, $method)
+    protected function _setIdempotencyHeader(&$query, $method)
     {
-        if (!isset($configuration->methods[$method])) {
-            return;
-        }
-        $fields = '';
-        if ($configuration->methods[$method]['idempotency']) {
-            $fields = $this->_getIdempotencyAttributes($configuration->attributes);
-        }
-        if ($fields != '') {
-            $query['headers']['x-idempotency-key'] = hash(self::$CIPHER, $fields);
+        if ($method != 'get' && $method != 'delete') {
+            if (array_key_exists('headers', array_change_key_case($query)) && !array_key_exists('x-idempotency-key', array_change_key_case($query['headers']))){
+                $query['headers']['x-idempotency-key'] = $this->_generateUUID();
+            }
         }
     }
     /**
-     * @param $attributes
-     *
-     * @return string
+     * _generateUUID()
      */
-    protected function _getIdempotencyAttributes($attributes)
+    protected function _generateUUID()
     {
-        $result = [];
-        foreach ($attributes as $key => $value) {
-            if ($value['idempotency']) {
-                $result[] = $key;
-            }
-        }
-        return implode('&', $result);
+        return sprintf(
+            '%04x%04x-%04x-%04x-%04x-%04x%04x%04x',
+            // 32 bits for "time_low"
+            mt_rand(0, 0xffff),
+            mt_rand(0, 0xffff),
+
+            // 16 bits for "time_mid"
+            mt_rand(0, 0xffff),
+
+            // 16 bits for "time_hi_and_version",
+            // four most significant bits holds version number 4
+            mt_rand(0, 0x0fff) | 0x4000,
+
+            // 16 bits, 8 bits for "clk_seq_hi_res",
+            // 8 bits for "clk_seq_low",
+            // two most significant bits holds zero and one for variant DCE1.1
+            mt_rand(0, 0x3fff) | 0x8000,
+
+            // 48 bits for "node"
+            mt_rand(0, 0xffff),
+            mt_rand(0, 0xffff),
+            mt_rand(0, 0xffff)
+        );
     }
 }
\ No newline at end of file
diff --git a/src/MercadoPago/Version.php b/src/MercadoPago/Version.php
index 08e28ce5..508acc46 100755
--- a/src/MercadoPago/Version.php
+++ b/src/MercadoPago/Version.php
@@ -4,5 +4,5 @@
 class Version
 {
     public static
-        $_VERSION = '1.12.5';
+        $_VERSION = '1.12.6';
 }