diff --git a/ModelDescriber/ApplyOpenApiDiscriminatorTrait.php b/ModelDescriber/ApplyOpenApiDiscriminatorTrait.php
index dd551fd..d3e5fe9 100644
--- a/ModelDescriber/ApplyOpenApiDiscriminatorTrait.php
+++ b/ModelDescriber/ApplyOpenApiDiscriminatorTrait.php
@@ -21,18 +21,19 @@ use Symfony\Component\PropertyInfo\Type;
  * Open API schemas to support poly morphism.
  *
  * @see https://swagger.io/docs/specification/data-models/inheritance-and-polymorphism/
+ *
  * @internal
  */
 trait ApplyOpenApiDiscriminatorTrait
 {
     /**
-     * @param Model $model the model that's being described, This is used to pass groups and config
-     *        down to the children models in `oneOf`
-     * @param OA\Schema $schema The Open API schema to which `oneOf` and `discriminator` properties
-     *        will be added
-     * @param string $discriminatorProperty The property that determine which model will be unsierailized
-     * @param array<string, string> $typeMap the map of $discriminatorProperty values to their
-     *        types
+     * @param Model                 $model                 the model that's being described, This is used to pass groups and config
+     *                                                     down to the children models in `oneOf`
+     * @param OA\Schema             $schema                The Open API schema to which `oneOf` and `discriminator` properties
+     *                                                     will be added
+     * @param string                $discriminatorProperty The property that determine which model will be unsierailized
+     * @param array<string, string> $typeMap               the map of $discriminatorProperty values to their
+     *                                                     types
      */
     protected function applyOpenApiDiscriminator(
         Model $model,
@@ -40,7 +41,7 @@ trait ApplyOpenApiDiscriminatorTrait
         ModelRegistry $modelRegistry,
         string $discriminatorProperty,
         array $typeMap
-    ) : void {
+    ): void {
         $schema->oneOf = [];
         $schema->discriminator = new OA\Discriminator([]);
         $schema->discriminator->propertyName = $discriminatorProperty;
@@ -54,7 +55,6 @@ trait ApplyOpenApiDiscriminatorTrait
             ));
             $schema->oneOf[] = $oneOfSchema;
             $schema->discriminator->mapping[$propertyValue] = clone $oneOfSchema;
-
         }
     }
 }
diff --git a/ModelDescriber/ObjectModelDescriber.php b/ModelDescriber/ObjectModelDescriber.php
index 893ae96..5260da8 100644
--- a/ModelDescriber/ObjectModelDescriber.php
+++ b/ModelDescriber/ObjectModelDescriber.php
@@ -74,7 +74,7 @@ class ObjectModelDescriber implements ModelDescriberInterface, ModelRegistryAwar
         $annotationsReader->updateDefinition($reflClass, $schema);
 
         $discriminatorMap = $this->doctrineReader->getClassAnnotation($reflClass, DiscriminatorMap::class);
-        if ($discriminatorMap && $schema->discriminator === OA\UNDEFINED) {
+        if ($discriminatorMap && OA\UNDEFINED === $schema->discriminator) {
             $this->applyOpenApiDiscriminator(
                 $model,
                 $schema,
diff --git a/Tests/ModelDescriber/ApplyOpenApiDiscriminatorTraitTest.php b/Tests/ModelDescriber/ApplyOpenApiDiscriminatorTraitTest.php
index 0644a8b..9ad9c8a 100644
--- a/Tests/ModelDescriber/ApplyOpenApiDiscriminatorTraitTest.php
+++ b/Tests/ModelDescriber/ApplyOpenApiDiscriminatorTraitTest.php
@@ -11,13 +11,12 @@
 
 namespace Nelmio\ApiDocBundle\Tests\ModelDescriber;
 
-use Doctrine\Common\Annotations\AnnotationReader;
 use Nelmio\ApiDocBundle\Model\Model;
 use Nelmio\ApiDocBundle\Model\ModelRegistry;
 use Nelmio\ApiDocBundle\ModelDescriber\ApplyOpenApiDiscriminatorTrait;
 use OpenApi\Annotations as OA;
-use Symfony\Component\PropertyInfo\Type;
 use PHPUnit\Framework\TestCase;
+use Symfony\Component\PropertyInfo\Type;
 
 class ApplyOpenApiDiscriminatorTraitTest extends TestCase
 {
@@ -70,14 +69,14 @@ class ApplyOpenApiDiscriminatorTraitTest extends TestCase
         );
     }
 
-    protected function setUp() : void
+    protected function setUp(): void
     {
         $this->schema = new OA\Schema([]);
         $this->model = $this->createModel(__CLASS__);
         $this->modelRegistry = new ModelRegistry([], new OA\OpenApi([]));
     }
 
-    private function createModel(string $className) : Model
+    private function createModel(string $className): Model
     {
         return new Model(
             new Type(Type::BUILTIN_TYPE_OBJECT, false, $className),