diff --git a/src/Controller/UserController.php b/src/Controller/UserController.php
index 96b52ec..7f3f974 100644
--- a/src/Controller/UserController.php
+++ b/src/Controller/UserController.php
@@ -5,12 +5,11 @@ namespace App\Controller;
 use App\Form\{CreateUserRequestType};
 use App\FormRequest\CreateUserRequest;
 use App\Repository\InviteRepository;
-use App\User\Exception\InvalidInviteException;
 use App\User\{InviteManager, UserManager};
 use Doctrine\ORM\EntityManagerInterface;
 use Symfony\Bundle\FrameworkBundle\Controller\Controller;
 use Symfony\Component\Form\Extension\Core\Type\SubmitType;
-use Symfony\Component\Form\{FormError, FormInterface};
+use Symfony\Component\Form\FormInterface;
 use Symfony\Component\HttpFoundation\{Request, Response};
 
 class UserController extends Controller
@@ -26,30 +25,19 @@ class UserController extends Controller
         $createUserRequest = new CreateUserRequest($inviteCode);
         $form = $this->createRegisterForm($createUserRequest, $inviteCode);
 
-        $inviteInvalid = false;
-
-        if (null === $invite = $inviteRepo->findOneBy(['code' => $inviteCode, 'usedBy' => null])) {
-            $inviteInvalid = true;
-        }
+        $invite = $inviteRepo->findOneBy(['code' => $inviteCode, 'usedBy' => null]);
 
         $form->handleRequest($request);
 
         if ($form->isSubmitted() && $form->isValid()) {
-            try {
-                $user = $userManager->createUserByInvite(
-                    $createUserRequest->username,
-                    $createUserRequest->password,
-                    $createUserRequest->email,
-                    $invite
-                );
+            $user = $userManager->createUserByInvite(
+                $createUserRequest->username,
+                $createUserRequest->password,
+                $createUserRequest->email,
+                $invite
+            );
 
-                $inviteManager->createInvitesForUser($user);
-            } catch (InvalidInviteException $ex) {
-                // @FIXME refactor InvalidInviteException to proper validator
-                $form->get('inviteCode')->addError(new FormError('Invalid invite code'));
-
-                return $this->render('User/register.html.twig', ['form' => $form->createView()]);
-            }
+            $inviteManager->createInvitesForUser($user);
 
             $em->flush();
 
@@ -58,7 +46,7 @@ class UserController extends Controller
 
         return $this->render('User/register.html.twig', [
             'form' => $form->createView(),
-            'inviteInvalid' => $inviteInvalid,
+            'inviteValid' => $invite ? true : null,
         ]);
     }
 
diff --git a/src/FormRequest/CreateUserRequest.php b/src/FormRequest/CreateUserRequest.php
index 5e0b740..523429c 100644
--- a/src/FormRequest/CreateUserRequest.php
+++ b/src/FormRequest/CreateUserRequest.php
@@ -3,6 +3,7 @@
 namespace App\FormRequest;
 
 use Symfony\Component\Validator\Constraints as Assert;
+use App\Validator\Constraints as AppAssert;
 
 /**
  * @todo implement UniqueEntity constraint for DTO and use it here
@@ -37,6 +38,7 @@ class CreateUserRequest
      *
      * @Assert\NotBlank()
      * @Assert\Length(min="32", max="32")
+     * @AppAssert\ValidInvite()
      */
     public $inviteCode;
 
diff --git a/src/User/Exception/InvalidInviteException.php b/src/User/Exception/InvalidInviteException.php
index be497ae..827015a 100644
--- a/src/User/Exception/InvalidInviteException.php
+++ b/src/User/Exception/InvalidInviteException.php
@@ -2,7 +2,7 @@
 
 namespace App\User\Exception;
 
-class InvalidInviteException extends \Exception
+class InvalidInviteException extends \InvalidArgumentException
 {
     protected $message = 'Invalid invite';
 }
\ No newline at end of file
diff --git a/src/Validator/Constraints/ValidInvite.php b/src/Validator/Constraints/ValidInvite.php
new file mode 100644
index 0000000..1a0d455
--- /dev/null
+++ b/src/Validator/Constraints/ValidInvite.php
@@ -0,0 +1,19 @@
+<?php
+
+namespace App\Validator\Constraints;
+
+use Symfony\Component\Validator\Constraint;
+
+/**
+ * @Annotation
+ */
+class ValidInvite extends Constraint
+{
+    public $notFoundMessage = 'Invite {{ code }} not found.';
+    public $usedMessage = 'Invite {{ code }} is used.';
+
+    public function validatedBy(): string
+    {
+        return get_class($this).'Validator';
+    }
+}
\ No newline at end of file
diff --git a/src/Validator/Constraints/ValidInviteValidator.php b/src/Validator/Constraints/ValidInviteValidator.php
new file mode 100644
index 0000000..b192b69
--- /dev/null
+++ b/src/Validator/Constraints/ValidInviteValidator.php
@@ -0,0 +1,42 @@
+<?php
+
+namespace App\Validator\Constraints;
+
+use App\Entity\Invite;
+use App\Repository\InviteRepository;
+use Symfony\Component\Validator\{Constraint, ConstraintValidator};
+
+class ValidInviteValidator extends ConstraintValidator
+{
+    /** @var InviteRepository */
+    private $inviteRepo;
+
+    public function __construct(InviteRepository $inviteRepo)
+    {
+        $this->inviteRepo = $inviteRepo;
+    }
+
+    /**
+     * @param mixed $value
+     * @param ValidInvite $constraint
+     */
+    public function validate($value, Constraint $constraint)
+    {
+        /** @var Invite $invite */
+        if (null === $invite = $this->inviteRepo->findOneBy(['code' => $value])) {
+            $this->context->buildViolation($constraint->notFoundMessage)
+                ->setParameter('{{ code }}', $value)
+                ->addViolation()
+            ;
+
+            return;
+        }
+
+        if (null !== $invite->getUsedBy()) {
+            $this->context->buildViolation($constraint->usedMessage)
+                ->setParameter('{{ code }}', $value)
+                ->addViolation()
+            ;
+        }
+    }
+}
\ No newline at end of file
diff --git a/templates/User/register.html.twig b/templates/User/register.html.twig
index 600b184..472ee49 100644
--- a/templates/User/register.html.twig
+++ b/templates/User/register.html.twig
@@ -1,11 +1,11 @@
 {% extends 'base.html.twig' %}
 
 {% block content %}
-    {% if inviteInvalid %}
-    <h1>Invalid invite</h1>
-    {% else %}
+    {% if inviteValid %}
     <div id="form-register">
         {{ form(form) }}
     </div>
+    {% else %}
+    <h1>Invalid invite</h1>
     {% endif %}
 {% endblock %}
\ No newline at end of file