diff --git a/modules/openapi-generator/src/main/resources/php-symfony/Bundle.mustache b/modules/openapi-generator/src/main/resources/php-symfony/Bundle.mustache
index 83ef7afa0af..4a6ab902081 100644
--- a/modules/openapi-generator/src/main/resources/php-symfony/Bundle.mustache
+++ b/modules/openapi-generator/src/main/resources/php-symfony/Bundle.mustache
@@ -33,7 +33,7 @@ use {{invokerPackage}}\DependencyInjection\Compiler\{{bundleName}}ApiPass;
  */
 class {{bundleClassName}} extends Bundle
 {
-    public function build(ContainerBuilder $container)
+    public function build(ContainerBuilder $container): void
     {
         $container->addCompilerPass(new {{bundleName}}ApiPass());
     }
diff --git a/samples/server/petstore/php-symfony/SymfonyBundle-php/OpenAPIServerBundle.php b/samples/server/petstore/php-symfony/SymfonyBundle-php/OpenAPIServerBundle.php
index 61d3eb42108..6e871221943 100644
--- a/samples/server/petstore/php-symfony/SymfonyBundle-php/OpenAPIServerBundle.php
+++ b/samples/server/petstore/php-symfony/SymfonyBundle-php/OpenAPIServerBundle.php
@@ -43,7 +43,7 @@ use OpenAPI\Server\DependencyInjection\Compiler\OpenAPIServerApiPass;
  */
 class OpenAPIServerBundle extends Bundle
 {
-    public function build(ContainerBuilder $container)
+    public function build(ContainerBuilder $container): void
     {
         $container->addCompilerPass(new OpenAPIServerApiPass());
     }