diff --git a/composer.json b/composer.json
index 2b2a7bd9..c355791d 100644
--- a/composer.json
+++ b/composer.json
@@ -27,7 +27,8 @@
         "symfony/process": "^v4.2",
         "symfony/serializer": "^4.2",
         "doctrine/doctrine-bundle": "^1.10",
-        "doctrine/orm": "^2.6"
+        "doctrine/orm": "^2.6",
+        "dunglas/doctrine-json-odm": "^0.1.3"
     },
     "require-dev": {
         "phpunit/phpunit": "^7.4",
diff --git a/src/Command/ExecuteTaskCommand.php b/src/Command/ExecuteTaskCommand.php
index 4fd312f0..e0303c25 100644
--- a/src/Command/ExecuteTaskCommand.php
+++ b/src/Command/ExecuteTaskCommand.php
@@ -105,10 +105,8 @@ protected function execute(InputInterface $input, OutputInterface $output)
         $path = new Path();
         $path->add(null, null, [$workflow->getDefinition()->getInitialPlace()]);
 
-        $metaData = json_decode($task->getMetaData());
-
         try {
-            foreach ($generator->getAvailableTransitions($workflow, $subject, $metaData) as $transitionName) {
+            foreach ($generator->getAvailableTransitions($workflow, $subject, $task->getMetaData()) as $transitionName) {
                 try {
                     if (!$generator->applyTransition($workflow, $subject, $transitionName)) {
                         throw new Exception(sprintf('Generator %s generated transition %s that can not be applied', $task->getGenerator(), $transitionName));
diff --git a/src/Entity/Task.php b/src/Entity/Task.php
index afe193c7..29d338c3 100644
--- a/src/Entity/Task.php
+++ b/src/Entity/Task.php
@@ -75,11 +75,9 @@ class Task
     private $takeScreenshots = false;
 
     /**
-     * @ORM\Column(type="text")
-     * @Assert\NotBlank
-     * @MbtAssert\Json
+     * @ORM\Column(type="json_document", options={"jsonb": true}, nullable=true)
      */
-    private $metaData = '{}';
+    private $metaData;
 
     /**
      * @var \DateTime
@@ -215,7 +213,7 @@ public function getTakeScreenshots()
         return $this->takeScreenshots;
     }
 
-    public function setMetaData(string $metaData)
+    public function setMetaData($metaData)
     {
         $this->metaData = $metaData;
     }
diff --git a/src/Validator/Constraints/Json.php b/src/Validator/Constraints/Json.php
deleted file mode 100644
index c59ce592..00000000
--- a/src/Validator/Constraints/Json.php
+++ /dev/null
@@ -1,13 +0,0 @@
-<?php
-
-namespace Tienvx\Bundle\MbtBundle\Validator\Constraints;
-
-use Symfony\Component\Validator\Constraint;
-
-/**
- * @Annotation
- */
-class Json extends Constraint
-{
-    public $message = '"{{ string }}" is not a valid json string.';
-}
diff --git a/src/Validator/Constraints/JsonValidator.php b/src/Validator/Constraints/JsonValidator.php
deleted file mode 100644
index 577883df..00000000
--- a/src/Validator/Constraints/JsonValidator.php
+++ /dev/null
@@ -1,37 +0,0 @@
-<?php
-
-namespace Tienvx\Bundle\MbtBundle\Validator\Constraints;
-
-use Symfony\Component\Validator\Constraint;
-use Symfony\Component\Validator\ConstraintValidator;
-use Symfony\Component\Validator\Exception\UnexpectedTypeException;
-
-/**
- * @Annotation
- */
-class JsonValidator extends ConstraintValidator
-{
-    /**
-     * {@inheritdoc}
-     */
-    public function validate($value, Constraint $constraint)
-    {
-        if (!$constraint instanceof Json) {
-            throw new UnexpectedTypeException($constraint, __NAMESPACE__.'\Json');
-        }
-
-        if (null === $value || '' === $value) {
-            return;
-        }
-
-        if (!is_scalar($value) && !(is_object($value) && method_exists($value, '__toString'))) {
-            throw new UnexpectedTypeException($value, 'string');
-        }
-
-        if (!json_decode($value)) {
-            $this->context->buildViolation($constraint->message)
-                ->setParameter('{{ string }}', $this->formatValue($value))
-                ->addViolation();
-        }
-    }
-}
diff --git a/tests/Message/ReplayTaskMessageTest.php b/tests/Message/ReplayTaskMessageTest.php
index a9a35547..db4bcbab 100644
--- a/tests/Message/ReplayTaskMessageTest.php
+++ b/tests/Message/ReplayTaskMessageTest.php
@@ -63,7 +63,7 @@ public function testConsumeMessage(string $model, string $generator, string $red
         $task->setTitle('Test regression task');
         $task->setModel($model);
         $task->setGenerator($generator);
-        $task->setMetaData(json_encode(['bugId' => $bug->getId()]));
+        $task->setMetaData((object) ['bugId' => $bug->getId()]);
         $task->setReducer($reducer);
         $task->setTakeScreenshots(false);
         $entityManager->persist($task);
diff --git a/tests/app/src/AppKernel.php b/tests/app/src/AppKernel.php
index d9558f89..f9b29250 100644
--- a/tests/app/src/AppKernel.php
+++ b/tests/app/src/AppKernel.php
@@ -3,6 +3,7 @@
 namespace App;
 
 use Doctrine\Bundle\DoctrineBundle\DoctrineBundle;
+use Dunglas\DoctrineJsonOdm\Bundle\DunglasDoctrineJsonOdmBundle;
 use Symfony\Bundle\FrameworkBundle\FrameworkBundle;
 use Symfony\Bundle\MakerBundle\MakerBundle;
 use Symfony\Bundle\MonologBundle\MonologBundle;
@@ -23,6 +24,7 @@ public function registerBundles()
             new DoctrineBundle(),
             new MonologBundle(),
             new MakerBundle(),
+            new DunglasDoctrineJsonOdmBundle(),
             new TienvxMbtBundle(),
         );