diff --git a/Describer/ModelRegistryAwareTrait.php b/Describer/ModelRegistryAwareTrait.php
index 0c50189..3bcdeca 100644
--- a/Describer/ModelRegistryAwareTrait.php
+++ b/Describer/ModelRegistryAwareTrait.php
@@ -20,9 +20,6 @@ trait ModelRegistryAwareTrait
      */
     private $modelRegistry;
 
-    /**
-     * @param ModelRegistry $modelRegistry
-     */
     public function setModelRegistry(ModelRegistry $modelRegistry)
     {
         $this->modelRegistry = $modelRegistry;
diff --git a/ModelDescriber/FormModelDescriber.php b/ModelDescriber/FormModelDescriber.php
index 0d55193..07f5bcc 100644
--- a/ModelDescriber/FormModelDescriber.php
+++ b/ModelDescriber/FormModelDescriber.php
@@ -116,11 +116,8 @@ final class FormModelDescriber implements ModelDescriberInterface, ModelRegistry
                     break;
                 }
 
-                if (
-                    ($formType = $type->getInnerType()) &&
-                    ($formClass = get_class($formType)) &&
-                    !$this->isBuiltinType($formClass)   //don't check builtin types in Form component.
-                ) {
+                if ($type->getInnerType() && ($formClass = get_class($type->getInnerType())) && !$this->isBuiltinType($formClass)) {
+                    //if form type is not builtin in Form component.
                     $model = new Model(new Type(Type::BUILTIN_TYPE_OBJECT, false, $formClass));
                     $property->setRef($this->modelRegistry->register($model));
                     break;
@@ -136,13 +133,8 @@ final class FormModelDescriber implements ModelDescriberInterface, ModelRegistry
         }
     }
 
-    /**
-     * @param string $type
-     *
-     * @return bool
-     */
-    private function isBuiltinType(string $type) : bool
+    private function isBuiltinType(string $type): bool
     {
-        return strpos($type, 'Symfony\Component\Form\Extension\Core\Type') !== false;
+        return 0 === strpos($type, 'Symfony\Component\Form\Extension\Core\Type');
     }
 }
diff --git a/Tests/Functional/Controller/ApiController.php b/Tests/Functional/Controller/ApiController.php
index 7fe84fc..1a43d37 100644
--- a/Tests/Functional/Controller/ApiController.php
+++ b/Tests/Functional/Controller/ApiController.php
@@ -18,9 +18,9 @@ use Nelmio\ApiDocBundle\Annotation\Operation;
 use Nelmio\ApiDocBundle\Tests\Functional\Entity\Article;
 use Nelmio\ApiDocBundle\Tests\Functional\Entity\User;
 use Nelmio\ApiDocBundle\Tests\Functional\Form\DummyType;
+use Nelmio\ApiDocBundle\Tests\Functional\Form\UserType;
 use Sensio\Bundle\FrameworkExtraBundle\Configuration\Route;
 use Swagger\Annotations as SWG;
-use Nelmio\ApiDocBundle\Tests\Functional\Form\UserType;
 
 /**
  * @Route("/api")
diff --git a/Tests/Functional/Form/UserType.php b/Tests/Functional/Form/UserType.php
index d3b9b4a..8cf8742 100644
--- a/Tests/Functional/Form/UserType.php
+++ b/Tests/Functional/Form/UserType.php
@@ -1,11 +1,20 @@
 <?php
 
+/*
+ * This file is part of the NelmioApiDocBundle package.
+ *
+ * (c) Nelmio
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
 namespace Nelmio\ApiDocBundle\Tests\Functional\Form;
 
+use Nelmio\ApiDocBundle\Tests\Functional\Entity\User;
 use Symfony\Component\Form\AbstractType;
 use Symfony\Component\Form\FormBuilderInterface;
 use Symfony\Component\OptionsResolver\OptionsResolver;
-use Nelmio\ApiDocBundle\Tests\Functional\Entity\User;
 
 class UserType extends AbstractType
 {
@@ -17,7 +26,7 @@ class UserType extends AbstractType
     public function configureOptions(OptionsResolver $resolver)
     {
         $resolver->setDefaults([
-            'data_class' => User::class
+            'data_class' => User::class,
         ]);
     }
-}
\ No newline at end of file
+}
diff --git a/Tests/Functional/FunctionalTest.php b/Tests/Functional/FunctionalTest.php
index 9d087db..5d0380e 100644
--- a/Tests/Functional/FunctionalTest.php
+++ b/Tests/Functional/FunctionalTest.php
@@ -179,7 +179,7 @@ class FunctionalTest extends WebTestCase
         $this->assertEquals([
             'type' => 'object',
             'properties' => [
-                'dummy' => ['$ref' => '#/definitions/DummyType']
+                'dummy' => ['$ref' => '#/definitions/DummyType'],
             ],
             'required' => ['dummy'],
         ], $this->getModel('UserType')->toArray());