diff --git a/core/lib/Drupal/Core/DrupalKernel.php b/core/lib/Drupal/Core/DrupalKernel.php
index a5624d700435c8e7a939e179db0378a14556f07a..f07d081fad4304853c961750691761f0a533242a 100644
--- a/core/lib/Drupal/Core/DrupalKernel.php
+++ b/core/lib/Drupal/Core/DrupalKernel.php
@@ -192,7 +192,7 @@ public function registerBundles() {
       // When installing new modules, the modules in the list passed to
       // updateModules() do not yet have their namespace registered.
       $namespace = 'Drupal\\' . $module;
-      if (!isset($namespaces[$namespace]) && $this->moduleData($module)) {
+      if (empty($namespaces[$namespace]) && $this->moduleData($module)) {
         $path = dirname(DRUPAL_ROOT . '/' . $this->moduleData($module)->uri) . '/lib';
         $this->modulePaths[$module] = $path;
         $this->classLoader->registerNamespace($namespace, $path);
@@ -319,15 +319,20 @@ protected function initializeContainer() {
       // All namespaces must be registered before we attempt to use any service
       // from the container.
       $namespaces = $this->classLoader->getNamespaces();
+      $namespaces_revert = array();
       foreach ($this->container->getParameter('container.modules') as $module => $path) {
         $namespace = 'Drupal\\' . $module;
-        if (!isset($namespaces[$namespace])) {
+        if (empty($namespaces[$namespace])) {
           $this->classLoader->registerNamespace($namespace, $path);
+          $namespaces_revert[$namespace] = array();
         }
       }
       $module_list = $this->moduleList ?: $this->container->get('config.factory')->get('system.module')->load()->get('enabled');
       if (array_keys((array)$module_list) !== array_keys($this->container->getParameter('container.modules'))) {
         unset($this->container);
+        // Since 'container.modules' was incorrect, revert the classloader
+        // registrations, and allow buildContainer() to get it right.
+        $this->classLoader->registerNamespaces($namespaces_revert);
       }
     }
 
diff --git a/core/modules/system/lib/Drupal/system/Tests/Module/ClassLoaderTest.php b/core/modules/system/lib/Drupal/system/Tests/Module/ClassLoaderTest.php
index ea2026d0522d969d90bd7ed0d9060ade3d62d173..df59ea08d8aae98d7a992c536f9676896deeb85e 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Module/ClassLoaderTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Module/ClassLoaderTest.php
@@ -37,16 +37,10 @@ function testClassLoading() {
 
     module_disable(array('module_autoload_test'), FALSE);
     $this->resetAll();
-    // The first request after a module has been disabled will result in that
-    // module's namespace getting registered because the kernel registers all
-    // namespaces in the existing 'container.modules' parameter before checking
-    // whether the list of modules has changed and rebuilding the container.
-    // @todo Fix the behavior so that the namespace is not registered even on the
-    //   first request after disabling the module and revert this test to having
-    //   the assertion inside the loop. See http://drupal.org/node/1846376
+    // Check twice to test an unprimed and primed system_list() cache.
     for ($i=0; $i<2; $i++) {
       $this->drupalGet('module-test/class-loading');
+      $this->assertNoText($expected, 'Autoloader does not load classes from a disabled module.');
     }
-    $this->assertNoText($expected, 'Autoloader does not load classes from a disabled module.');
   }
 }