diff --git a/core/lib/Drupal/Component/Plugin/Discovery/DerivativeDiscoveryDecorator.php b/core/lib/Drupal/Component/Plugin/Discovery/DerivativeDiscoveryDecorator.php
index 027c59a..3437773 100644
--- a/core/lib/Drupal/Component/Plugin/Discovery/DerivativeDiscoveryDecorator.php
+++ b/core/lib/Drupal/Component/Plugin/Discovery/DerivativeDiscoveryDecorator.php
@@ -81,24 +81,31 @@ public function getDefinitions() {
    */
   protected function getDerivatives(array $base_plugin_definitions) {
     $plugin_definitions = array();
+    $derivative_plugin_definitions = array();
     foreach ($base_plugin_definitions as $base_plugin_id => $plugin_definition) {
       $derivative_fetcher = $this->getDerivativeFetcher($base_plugin_id, $plugin_definition);
       if ($derivative_fetcher) {
         $derivative_definitions = $derivative_fetcher->getDerivativeDefinitions($plugin_definition);
         foreach ($derivative_definitions as $derivative_id => $derivative_definition) {
           $plugin_id = $this->encodePluginId($base_plugin_id, $derivative_id);
-          // Use this definition as defaults if a plugin already defined
-          // itself as this derivative.
-          if ($derivative_id && isset($base_plugin_definitions[$plugin_id])) {
-            $derivative_definition = $base_plugin_definitions[$plugin_id] + ($derivative_definition ?: array());
-          }
           $plugin_definitions[$plugin_id] = $derivative_definition;
         }
       }
-      // If a plugin already defined itself as a derivative it might already
-      // be merged into the definitions.
-      elseif (!isset($plugin_definitions[$base_plugin_id])) {
-        $plugin_definitions[$base_plugin_id] = $plugin_definition;
+      else {
+        list(, $derivative_id) = $this->decodePluginId($base_plugin_id);
+        if ($derivative_id) {
+          $derivative_plugin_definitions[$base_plugin_id] = $plugin_definition;
+        }
+        else {
+          $plugin_definitions[$base_plugin_id] = $plugin_definition;
+        }
+      }
+    }
+    foreach ($derivative_plugin_definitions as $plugin_id => $plugin_definition) {
+      if (isset($plugin_definitions[$plugin_id])) {
+        // Use this definition as defaults if a plugin already defined
+        // itself as this derivative.
+        $plugin_definitions[$plugin_id] = $plugin_definition + $plugin_definitions[$plugin_id];
       }
     }
 
diff --git a/core/lib/Drupal/Core/Extension/ModuleHandler.php b/core/lib/Drupal/Core/Extension/ModuleHandler.php
index cbfd882..001e278 100644
--- a/core/lib/Drupal/Core/Extension/ModuleHandler.php
+++ b/core/lib/Drupal/Core/Extension/ModuleHandler.php
@@ -611,7 +611,6 @@ public function install(array $module_list, $enable_dependencies = TRUE) {
         // @todo install_begin_request() creates a container without a kernel.
         if ($kernel = \Drupal::service('kernel', ContainerInterface::NULL_ON_INVALID_REFERENCE)) {
           $kernel->updateModules($module_filenames, $module_filenames);
-          \Drupal::moduleHandler()->loadAll();
         }
 
         // Refresh the schema to include it.