core/modules/rest/src/Routing/ResourceRoutes.php | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/core/modules/rest/src/Routing/ResourceRoutes.php b/core/modules/rest/src/Routing/ResourceRoutes.php
index 1589bf4..f9cb648 100644
--- a/core/modules/rest/src/Routing/ResourceRoutes.php
+++ b/core/modules/rest/src/Routing/ResourceRoutes.php
@@ -72,6 +72,9 @@ protected function alterRoutes(RouteCollection $collection) {
     // @todo Remove in https://www.drupal.org/node/2308745
     $resources = $this->config->get('rest.settings')->get('resources') ?: array();
     $enabled_resources = array_intersect_key($resources, $this->manager->getDefinitions());
+    if (count($resources) != count($enabled_resources)) {
+      trigger_error('rest.settings lists resources relying on missing plugins.');
+    }
 
     // Iterate over all enabled resource plugins.
     foreach ($enabled_resources as $id => $enabled_methods) {