diff --git a/ModelDescriber/ObjectModelDescriber.php b/ModelDescriber/ObjectModelDescriber.php
index 8c726c9..56a1fdb 100644
--- a/ModelDescriber/ObjectModelDescriber.php
+++ b/ModelDescriber/ObjectModelDescriber.php
@@ -110,6 +110,8 @@ class ObjectModelDescriber implements ModelDescriberInterface, ModelRegistryAwar
                     $property->setType('string');
                     $property->setFormat('date-time');
                 } else {
+                    $type = new Type($type->getBuiltinType(), false, $type->getClassName(), $type->isCollection(), $type->getCollectionKeyType(), $type->getCollectionValueType()); // ignore nullable field
+
                     $property->setRef(
                         $this->modelRegistry->register(new Model($type, $model->getGroups()))
                     );
diff --git a/Tests/Functional/Entity/User.php b/Tests/Functional/Entity/User.php
index 43643eb..bb03ea4 100644
--- a/Tests/Functional/Entity/User.php
+++ b/Tests/Functional/Entity/User.php
@@ -66,6 +66,11 @@ class User
      */
     private $users;
 
+    /**
+     * @var User|null
+     */
+    private $friend;
+
     /**
      * @var string
      *
@@ -118,6 +123,10 @@ class User
     {
     }
 
+    public function setFriend(self $friend = null)
+    {
+    }
+
     public function setDummy(Dummy $dummy)
     {
     }
diff --git a/Tests/Functional/FunctionalTest.php b/Tests/Functional/FunctionalTest.php
index 95d8071..dbd2012 100644
--- a/Tests/Functional/FunctionalTest.php
+++ b/Tests/Functional/FunctionalTest.php
@@ -41,6 +41,8 @@ class FunctionalTest extends WebTestCase
         $modelProperties = $this->getModel('Article')->getProperties();
         $this->assertCount(1, $modelProperties);
         $this->assertTrue($modelProperties->has('author'));
+        $this->assertSame('#/definitions/User2', $modelProperties->get('author')->getRef());
+
         $this->assertFalse($modelProperties->has('content'));
     }
 
@@ -209,6 +211,9 @@ class FunctionalTest extends WebTestCase
                         ],
                         'type' => 'array',
                     ],
+                    'friend' => [
+                        '$ref' => '#/definitions/User',
+                    ],
                     'dummy' => [
                         '$ref' => '#/definitions/Dummy2',
                     ],