diff --git a/ModelDescriber/FormModelDescriber.php b/ModelDescriber/FormModelDescriber.php
index 15fd27a..5c8dafc 100644
--- a/ModelDescriber/FormModelDescriber.php
+++ b/ModelDescriber/FormModelDescriber.php
@@ -75,7 +75,10 @@ final class FormModelDescriber implements ModelDescriberInterface, ModelRegistry
                 $schema->setRequired($required);
             }
 
-            $property->merge($config->getOption('documentation'));
+            if ($config->hasOption('documentation')) {
+                $property->merge($config->getOption('documentation'));
+            }
+
             if (null !== $property->getType()) {
                 continue; // Type manually defined
             }
diff --git a/Tests/Functional/Form/UserType.php b/Tests/Functional/Form/UserType.php
index c0c02f0..a60bf56 100644
--- a/Tests/Functional/Form/UserType.php
+++ b/Tests/Functional/Form/UserType.php
@@ -14,6 +14,7 @@ namespace Nelmio\ApiDocBundle\Tests\Functional\Form;
 use Nelmio\ApiDocBundle\Tests\Functional\Entity\User;
 use Symfony\Component\Form\AbstractType;
 use Symfony\Component\Form\Extension\Core\Type\CollectionType;
+use Symfony\Component\Form\Extension\Core\Type\SubmitType;
 use Symfony\Component\Form\Extension\Core\Type\TextType;
 use Symfony\Component\Form\FormBuilderInterface;
 use Symfony\Component\OptionsResolver\OptionsResolver;
@@ -40,7 +41,8 @@ class UserType extends AbstractType
             ->add('entities', EntityType::class, ['class' => 'Entity', 'multiple' => true])
             ->add('document', DocumentType::class, ['class' => 'Document'])
             ->add('documents', DocumentType::class, ['class' => 'Document', 'multiple' => true])
-            ->add('extended_builtin', ExtendedBuiltinType::class, ['required_option' => 'foo']);
+            ->add('extended_builtin', ExtendedBuiltinType::class, ['required_option' => 'foo'])
+            ->add('save', SubmitType::class);
     }
 
     public function configureOptions(OptionsResolver $resolver)
diff --git a/Tests/Functional/FunctionalTest.php b/Tests/Functional/FunctionalTest.php
index db6c235..282a34d 100644
--- a/Tests/Functional/FunctionalTest.php
+++ b/Tests/Functional/FunctionalTest.php
@@ -274,6 +274,8 @@ class FunctionalTest extends WebTestCase
                     'type' => 'string',
                     'enum' => ['foo', 'bar'],
                 ],
+                'save' => [
+                ],
             ],
             'required' => ['dummy', 'dummies', 'entity', 'entities', 'document', 'documents', 'extended_builtin'],
         ], $this->getModel('UserType')->toArray());