diff --git a/CHANGELOG.md b/CHANGELOG.md
index bf64357..52e1278 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,7 @@ CHANGELOG
 3.7.0
 -----
 
+* remove pattern added from the Expression Violation message.
 * Added `@SerializedName` annotation support and name converters when using Symfony >= 4.2.
 
 3.3.0
diff --git a/Describer/OpenApiPhpDescriber.php b/Describer/OpenApiPhpDescriber.php
index 128a529..938e471 100644
--- a/Describer/OpenApiPhpDescriber.php
+++ b/Describer/OpenApiPhpDescriber.php
@@ -69,7 +69,7 @@ final class OpenApiPhpDescriber
                 return $v instanceof OA\AbstractAnnotation;
             });
 
-            if (0 === count($annotations)) {
+            if (0 === count($annotations) && 0 === count($classAnnotations[$declaringClass->getName()])) {
                 continue;
             }
 
diff --git a/ModelDescriber/Annotations/SymfonyConstraintAnnotationReader.php b/ModelDescriber/Annotations/SymfonyConstraintAnnotationReader.php
index e8eb58d..3580f48 100644
--- a/ModelDescriber/Annotations/SymfonyConstraintAnnotationReader.php
+++ b/ModelDescriber/Annotations/SymfonyConstraintAnnotationReader.php
@@ -69,8 +69,6 @@ class SymfonyConstraintAnnotationReader
             } elseif ($annotation instanceof Assert\Choice) {
                 $values = $annotation->callback ? call_user_func(is_array($annotation->callback) ? $annotation->callback : [$reflectionProperty->class, $annotation->callback]) : $annotation->choices;
                 $property->enum = array_values($values);
-            } elseif ($annotation instanceof Assert\Expression) {
-                $this->appendPattern($property, $annotation->message);
             } elseif ($annotation instanceof Assert\Range) {
                 $property->minimum = (int) $annotation->min;
                 $property->maximum = (int) $annotation->max;
diff --git a/ModelDescriber/ObjectModelDescriber.php b/ModelDescriber/ObjectModelDescriber.php
index 94a37f6..8036bb8 100644
--- a/ModelDescriber/ObjectModelDescriber.php
+++ b/ModelDescriber/ObjectModelDescriber.php
@@ -61,9 +61,9 @@ class ObjectModelDescriber implements ModelDescriberInterface, ModelRegistryAwar
         $class = $model->getType()->getClassName();
         $schema->_context->class = $class;
 
-        $context = [];
+        $context = ['serializer_groups' => null];
         if (null !== $model->getGroups()) {
-            $context = ['serializer_groups' => array_filter($model->getGroups(), 'is_string')];
+            $context['serializer_groups'] = array_filter($model->getGroups(), 'is_string');
         }
 
         $annotationsReader = new AnnotationsReader($this->doctrineReader, $this->modelRegistry, $this->mediaTypes);
diff --git a/Tests/Functional/Controller/InvokableController.php b/Tests/Functional/Controller/InvokableController.php
new file mode 100644
index 0000000..b640b70
--- /dev/null
+++ b/Tests/Functional/Controller/InvokableController.php
@@ -0,0 +1,31 @@
+<?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\Controller;
+
+use OpenApi\Annotations as OA;
+use Symfony\Component\Routing\Annotation\Route;
+
+/**
+ * Prevents a regression (see https://github.com/nelmio/NelmioApiDocBundle/issues/1559).
+ *
+ * @Route("/api/invoke", host="api.example.com", name="invokable", methods={"GET"})
+ * @OA\Response(
+ *    response=200,
+ *    description="Invokable!"
+ * )
+ */
+class InvokableController
+{
+    public function __invoke()
+    {
+    }
+}
diff --git a/Tests/Functional/FunctionalTest.php b/Tests/Functional/FunctionalTest.php
index 8b8c7dd..5fc871a 100644
--- a/Tests/Functional/FunctionalTest.php
+++ b/Tests/Functional/FunctionalTest.php
@@ -374,7 +374,6 @@ class FunctionalTest extends WebTestCase
                 ],
                 'propertyExpression' => [
                     'type' => 'integer',
-                    'pattern' => 'If this is a tech post, the category should be either php or symfony!',
                 ],
                 'propertyRange' => [
                     'type' => 'integer',
@@ -449,4 +448,10 @@ class FunctionalTest extends WebTestCase
         $this->assertSame('array', $property->oneOf[1]->type);
         $this->assertSame('#/components/schemas/CompoundEntity', $property->oneOf[1]->items->ref);
     }
+
+    public function testInvokableController()
+    {
+        $operation = $this->getOperation('/api/invoke', 'get');
+        $this->assertSame('Invokable!', $this->getOperationResponse($operation, 200)->description);
+    }
 }
diff --git a/Tests/Functional/TestKernel.php b/Tests/Functional/TestKernel.php
index 6b9dbf6..57b5674 100644
--- a/Tests/Functional/TestKernel.php
+++ b/Tests/Functional/TestKernel.php
@@ -81,6 +81,7 @@ class TestKernel extends Kernel
         $routes->import(__DIR__.'/Controller/ApiController.php', '/', 'annotation');
         $routes->import(__DIR__.'/Controller/ClassApiController.php', '/', 'annotation');
         $routes->import(__DIR__.'/Controller/UndocumentedController.php', '/', 'annotation');
+        $routes->import(__DIR__.'/Controller/InvokableController.php', '/', 'annotation');
         $routes->import('', '/api', 'api_platform');
         $routes->add('/docs/{area}', 'nelmio_api_doc.controller.swagger_ui')->setDefault('area', 'default');
         $routes->add('/docs.json', 'nelmio_api_doc.controller.swagger');