diff --git a/setup/src/Magento/Setup/Model/PackagesAuth.php b/setup/src/Magento/Setup/Model/PackagesAuth.php
index 88a63b5e6f679..5a29f9953d51b 100644
--- a/setup/src/Magento/Setup/Model/PackagesAuth.php
+++ b/setup/src/Magento/Setup/Model/PackagesAuth.php
@@ -49,19 +49,29 @@ class PackagesAuth
      */
     private $filesystem;
 
+    /**
+     * @var \Magento\Framework\Serialize\Serializer\Json
+     */
+    private $serializer;
+
     /**
      * @param \Zend\ServiceManager\ServiceLocatorInterface $serviceLocator
      * @param \Magento\Framework\HTTP\Client\Curl $curl
      * @param \Magento\Framework\Filesystem $filesystem
+     * @param \Magento\Framework\Serialize\Serializer\Json|null $serializer
+     * @throws \RuntimeException
      */
     public function __construct(
         \Zend\ServiceManager\ServiceLocatorInterface $serviceLocator,
         \Magento\Framework\HTTP\Client\Curl $curl,
-        \Magento\Framework\Filesystem $filesystem
+        \Magento\Framework\Filesystem $filesystem,
+        \Magento\Framework\Serialize\Serializer\Json $serializer = null
     ) {
         $this->serviceLocator = $serviceLocator;
         $this->curlClient = $curl;
         $this->filesystem = $filesystem;
+        $this->serializer = $serializer?: \Magento\Framework\App\ObjectManager::getInstance()
+            ->get(\Magento\Framework\Serialize\Serializer\Json::class);
     }
 
     /**
@@ -85,9 +95,11 @@ public function getCredentialBaseUrl()
      * @param string $token
      * @param string $secretKey
      * @return string
+     * @throws \InvalidArgumentException
      */
     public function checkCredentials($token, $secretKey)
     {
+        $response = ['success' => true];
         $serviceUrl = $this->getPackagesJsonUrl();
         $this->curlClient->setCredentials($token, $secretKey);
         try {
@@ -96,13 +108,13 @@ public function checkCredentials($token, $secretKey)
                 $packagesInfo = $this->curlClient->getBody();
                 $directory = $this->filesystem->getDirectoryWrite(DirectoryList::COMPOSER_HOME);
                 $directory->writeFile(self::PATH_TO_PACKAGES_FILE, $packagesInfo);
-                return \Zend_Json::encode(['success' => true]);
             } else {
-                return \Zend_Json::encode(['success' => false, 'message' => 'Bad credentials']);
+                $response = ['success' => false, 'message' => 'Bad credentials'];
             }
         } catch (\Exception $e) {
-            return \Zend_Json::encode(['success' => false, 'message' => $e->getMessage()]);
+            $response = ['success' => false, 'message' => $e->getMessage()];
         }
+        return $this->serializer->serialize($response);
     }
 
     /**
diff --git a/setup/src/Magento/Setup/Test/Unit/Model/PackagesAuthTest.php b/setup/src/Magento/Setup/Test/Unit/Model/PackagesAuthTest.php
index 67307e3adfcef..2c7d6d715d770 100644
--- a/setup/src/Magento/Setup/Test/Unit/Model/PackagesAuthTest.php
+++ b/setup/src/Magento/Setup/Test/Unit/Model/PackagesAuthTest.php
@@ -28,6 +28,9 @@ class PackagesAuthTest extends \PHPUnit_Framework_TestCase
      */
     private $packagesAuth;
 
+    /** @var \Magento\Framework\Serialize\Serializer\Json|\PHPUnit_Framework_MockObject_MockObject */
+    private $serializerMock;
+
     public function setUp()
     {
         $zendServiceLocator = $this->getMock(\Zend\ServiceManager\ServiceLocatorInterface::class, [], [], '', false);
@@ -42,7 +45,21 @@ public function setUp()
             ]);
         $this->curl = $this->getMock(\Magento\Framework\HTTP\Client\Curl::class, [], [], '', false);
         $this->filesystem = $this->getMock(\Magento\Framework\Filesystem::class, [], [], '', false);
-        $this->packagesAuth = new PackagesAuth($zendServiceLocator, $this->curl, $this->filesystem);
+        $this->serializerMock = $this->getMockBuilder(\Magento\Framework\Serialize\Serializer\Json::class)
+            ->getMock();
+        $this->serializerMock->expects($this->any())
+            ->method('serialize')
+            ->willReturnCallback(
+                function ($serializedData) {
+                    return json_encode($serializedData);
+                }
+            );
+        $this->packagesAuth = new PackagesAuth(
+            $zendServiceLocator,
+            $this->curl,
+            $this->filesystem,
+            $this->serializerMock
+        );
     }
 
     public function testCheckCredentialsActionBadCredentials()