diff --git a/CHANGELOG.md b/CHANGELOG.md
index 52f163a0..f62f2950 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,8 @@
 ChangeLog
 =========
+1.6.1
+-------------------
+Added custom headers
 
 1.6.0
 -------------------
diff --git a/README.md b/README.md
index 58c9c5ec..e311a118 100644
--- a/README.md
+++ b/README.md
@@ -6,7 +6,7 @@ Hyperwallet REST SDK (Beta)
 ===========================
 
 A library to manage users, transfer methods and payments through the Hyperwallet Rest V3 API
-For Rest V4 APIs, please use SDK v2.1.0
+For Rest V4 APIs, please use SDK v2.x.x
 
 Prerequisites
 ------------
diff --git a/src/Hyperwallet/Hyperwallet.php b/src/Hyperwallet/Hyperwallet.php
index 67c785f6..aaf644c6 100644
--- a/src/Hyperwallet/Hyperwallet.php
+++ b/src/Hyperwallet/Hyperwallet.php
@@ -68,13 +68,13 @@ class Hyperwallet {
      *
      * @throws HyperwalletArgumentException
      */
-    public function __construct($username, $password, $programToken = null, $server = 'https://api.sandbox.hyperwallet.com', $encryptionData = array()) {
+    public function __construct($username, $password, $programToken = null, $server = 'https://api.sandbox.hyperwallet.com', $encryptionData = array(), $clientOptions = array()) {
         if (empty($username) || empty($password)) {
             throw new HyperwalletArgumentException('You need to specify your API username and password!');
         }
 
         $this->programToken = $programToken;
-        $this->client = new ApiClient($username, $password, $server, array(), $encryptionData);
+        $this->client = new ApiClient($username, $password, $server, $clientOptions, $encryptionData);
     }
 
     //--------------------------------------
diff --git a/src/Hyperwallet/Util/ApiClient.php b/src/Hyperwallet/Util/ApiClient.php
index 1bbf326a..2580daef 100644
--- a/src/Hyperwallet/Util/ApiClient.php
+++ b/src/Hyperwallet/Util/ApiClient.php
@@ -9,6 +9,7 @@
 use Hyperwallet\Model\BaseModel;
 use Hyperwallet\Response\ErrorResponse;
 use Hyperwallet\Util\HyperwalletEncryption;
+use Hyperwallet\Util\HyperwalletUUID;
 
 /**
  * The internal API client
@@ -22,7 +23,7 @@ class ApiClient {
      *
      * @var string
      */
-    const VERSION = '1.6.0';
+    const VERSION = '1.6.1';
 
     /**
      * The Guzzle http client
@@ -38,6 +39,13 @@ class ApiClient {
      */
     private $encryption;
 
+    /**
+     * The UUID generator for http request/response
+     *
+     * @var HyperwalletUUID
+     */
+    private $uuid;
+
     /**
      * Boolean flag that checks if ApiClient is constructed with encryption enabled or not
      *
@@ -55,14 +63,17 @@ class ApiClient {
      * @param array $encryptionData Encryption data to initialize ApiClient with encryption enabled
      */
     public function __construct($username, $password, $server, $clientOptions = array(), $encryptionData = array()) {
+        $this->uuid = HyperwalletUUID::v4();
         // Setup http client if not specified
         $this->client = new Client(array_merge_recursive(array(
             'base_uri' => $server,
             'auth' => array($username, $password),
             'headers' => array(
                 'User-Agent' => 'Hyperwallet PHP SDK v' . self::VERSION,
-                'Accept' => 'application/json'
-            )
+                'Accept' => 'application/json',
+                'x-sdk-version' => self::VERSION,
+                'x-sdk-type' => 'PHP',
+                'x-sdk-contextId' => $this->uuid)
         ), $clientOptions));
         if (!empty($encryptionData) && isset($encryptionData['clientPrivateKeySetLocation']) &&
             isset($encryptionData['hyperwalletKeySetLocation'])) {
diff --git a/src/Hyperwallet/Util/HyperwalletUUID.php b/src/Hyperwallet/Util/HyperwalletUUID.php
new file mode 100644
index 00000000..8c803c7f
--- /dev/null
+++ b/src/Hyperwallet/Util/HyperwalletUUID.php
@@ -0,0 +1,57 @@
+<?php
+namespace Hyperwallet\Util;
+use GuzzleHttp\Client;
+use GuzzleHttp\Exception\BadResponseException;
+use GuzzleHttp\Exception\ConnectException;
+use GuzzleHttp\UriTemplate;
+use Hyperwallet\Exception\HyperwalletApiException;
+use Hyperwallet\Exception\HyperwalletException;
+use Hyperwallet\Model\BaseModel;
+use Hyperwallet\Response\ErrorResponse;
+use Composer\Autoload\ClassLoader;
+use phpseclib\Crypt\RSA;
+use phpseclib\Math\BigInteger;
+use phpseclib\Crypt\Hash;
+use JOSE_URLSafeBase64;
+use JOSE_JWS;
+use JOSE_JWE;
+use JOSE_JWK;
+use JOSE_JWT;
+
+/**
+ * The encryption service for Hyperwallet client's requests/responses
+ *
+ * @package Hyperwallet\Util
+ */
+class HyperwalletUUID {
+
+    /**
+     * Generates UUID
+     *
+     * @return string
+     *
+     * @throws HyperwalletException
+     */
+    public static function v4() {
+        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)
+        );
+    }
+}
diff --git a/tests/Hyperwallet/Tests/HyperwalletTest.php b/tests/Hyperwallet/Tests/HyperwalletTest.php
index 36cef9e3..23bff175 100644
--- a/tests/Hyperwallet/Tests/HyperwalletTest.php
+++ b/tests/Hyperwallet/Tests/HyperwalletTest.php
@@ -33,8 +33,6 @@
 
 class HyperwalletTest extends \PHPUnit_Framework_TestCase {
 
-    private $includeIntegrationTest = false; //change this value to true if integration tests have to be run
-
     public function testConstructor_throwErrorIfUsernameIsEmpty() {
         try {
             new Hyperwallet('', 'test-password');
diff --git a/tests/Hyperwallet/Tests/Util/ApiClientTest.php b/tests/Hyperwallet/Tests/Util/ApiClientTest.php
index 20c6a046..54ba6b61 100644
--- a/tests/Hyperwallet/Tests/Util/ApiClientTest.php
+++ b/tests/Hyperwallet/Tests/Util/ApiClientTest.php
@@ -929,7 +929,7 @@ private function validateRequest($method, $path, $query, array $body, $hasConten
         $request = $this->container[0]['request'];
         $this->assertEquals($method, $request->getMethod());
 
-        $this->assertCount(($hasContentType ? 6 : 4) + count($headers), $request->getHeaders());
+        $this->assertCount(($hasContentType ? 9 : 7) + count($headers), $request->getHeaders());
         $this->assertArrayHasKeyAndValue('Accept', $isEncrypted ? 'application/jose+json' : 'application/json', $request->getHeaders());
         if ($hasContentType) {
             $this->assertArrayHasKeyAndValue('Content-Type', $isEncrypted ? 'application/jose+json' : 'application/json', $request->getHeaders());
diff --git a/tests/Hyperwallet/Tests/Util/HyperwalletEncryptionTest.php b/tests/Hyperwallet/Tests/Util/HyperwalletEncryptionTest.php
index 98b7ef06..e491cd8e 100644
--- a/tests/Hyperwallet/Tests/Util/HyperwalletEncryptionTest.php
+++ b/tests/Hyperwallet/Tests/Util/HyperwalletEncryptionTest.php
@@ -1,5 +1,5 @@
 <?php
-namespace Hyperwallet\Tests;
+namespace Hyperwallet\Tests\Util;
 
 use Hyperwallet\Util\HyperwalletEncryption;
 use Hyperwallet\Exception\HyperwalletException;
diff --git a/tests/Hyperwallet/Tests/Util/HyperwalletUUIDTest.php b/tests/Hyperwallet/Tests/Util/HyperwalletUUIDTest.php
new file mode 100644
index 00000000..83bca552
--- /dev/null
+++ b/tests/Hyperwallet/Tests/Util/HyperwalletUUIDTest.php
@@ -0,0 +1,23 @@
+<?php
+namespace Hyperwallet\Tests\Util;
+
+use Hyperwallet\Exception\HyperwalletException;
+use Hyperwallet\Util\HyperwalletUUID;
+
+class HyperwalletUUIDTest extends \PHPUnit_Framework_TestCase {
+
+    public function testShouldSuccessfullyGenerateRandomUUIDs() {
+        // Setup data
+        $UUIDUtility = new HyperwalletUUID();
+
+        // Execute test
+        $uuid1 = $UUIDUtility->v4();
+        $uuid2 = $UUIDUtility->v4();
+        $uuid3 = $UUIDUtility->v4();
+
+        // Validate result
+        $this->assertNotEquals($uuid1, $uuid2);
+        $this->assertNotEquals($uuid2, $uuid3);
+        $this->assertNotEquals($uuid3, $uuid1);
+    }
+}
\ No newline at end of file