diff --git a/core/modules/rest/src/Routing/ResourceRoutes.php b/core/modules/rest/src/Routing/ResourceRoutes.php
index f3e64bd..509b953 100644
--- a/core/modules/rest/src/Routing/ResourceRoutes.php
+++ b/core/modules/rest/src/Routing/ResourceRoutes.php
@@ -126,7 +126,8 @@ protected function getRoutesForResourceConfig(RestResourceConfigInterface $rest_
         }
         $route->setOption('_auth', $rest_resource_config->getAuthenticationProviders($method));
         $route->setDefault('_rest_resource_config', $rest_resource_config->id());
-        $route->setOption('parameters', $route->getOption('parameters') + [
+        $parameters = $route->getOption('parameters') ?: [];
+        $route->setOption('parameters', $parameters + [
           '_rest_resource_config' => [
             'type' => 'entity:' . $rest_resource_config->getEntityTypeId(),
           ],