diff --git a/core/modules/serialization/src/RegisterEntityResolversCompilerPass.php b/core/modules/serialization/src/RegisterEntityResolversCompilerPass.php
index 8d4d3af9e4da4d302e61cd68b5be51466a4fa740..c495b700dd38d962a4f511710621e25a5d413487 100644
--- a/core/modules/serialization/src/RegisterEntityResolversCompilerPass.php
+++ b/core/modules/serialization/src/RegisterEntityResolversCompilerPass.php
@@ -17,7 +17,7 @@ class RegisterEntityResolversCompilerPass implements CompilerPassInterface {
    * @param \Symfony\Component\DependencyInjection\ContainerBuilder $container
    *   The container to process.
    */
-  public function process(ContainerBuilder $container) {
+  public function process(ContainerBuilder $container): void {
     $definition = $container->getDefinition('serializer.entity_resolver');
     $resolvers = [];