diff --git a/core/lib/Drupal/Core/Template/TwigExtension.php b/core/lib/Drupal/Core/Template/TwigExtension.php
index 551e3cb..f7991be 100644
--- a/core/lib/Drupal/Core/Template/TwigExtension.php
+++ b/core/lib/Drupal/Core/Template/TwigExtension.php
@@ -69,6 +69,9 @@ public function setLinkGenerator(LinkGeneratorInterface $link_generator) {
   public function getFunctions() {
     return array(
       // This function will receive a renderable array, if an array is detected.
+      new \Twig_SimpleFunction('render', 'twig_render_var'),
+      // render and render_var do the same thing. render_var is only kept for
+      // backwards compatibility.
       new \Twig_SimpleFunction('render_var', 'twig_render_var'),
       // The url and path function are defined in close parallel to those found
       // in \Symfony\Bridge\Twig\Extension\RoutingExtension
diff --git a/core/modules/system/src/Tests/Theme/TwigFunctionTest.php b/core/modules/system/src/Tests/Theme/TwigFunctionTest.php
new file mode 100644
index 0000000..0f76a5f
--- /dev/null
+++ b/core/modules/system/src/Tests/Theme/TwigFunctionTest.php
@@ -0,0 +1,57 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\system\Tests\Theme\TwigFunctionTest.
+ */
+
+namespace Drupal\system\Tests\Theme;
+
+use Drupal\simpletest\KernelTestBase;
+
+/**
+ * Tests Drupal's Twig functions.
+ *
+ * @group Theme
+ */
+class TwigFunctionTest extends KernelTestBase {
+
+  /**
+   * Modules to enable.
+   *
+   * @var array
+   */
+  public static $modules = ['system'];
+
+  /**
+   * Tests the Twig 'render' function.
+   */
+  public function testTwigRenderFunction() {
+    $element = [
+      '#type' => 'inline_template',
+      '#template' => '{% set cats = render(animals.some_cats_i_know) %}{{ cats }}',
+      '#context' => ['animals' => [
+        'some_cats_i_know' => [
+          '#theme' => 'item_list',
+          '#title' => t('Some cats I know'),
+          '#items' => [
+            'Wyatt',
+            'Puck',
+          ],
+        ],
+        'some_dogs_i_know' => [
+          '#theme' => 'item_list',
+          '#title' => t('Some dogs I know'),
+          '#items' => [
+            'Otis',
+            'Peanut',
+          ],
+        ],
+      ]],
+    ];
+
+    $rendered = \Drupal::service('renderer')->render($element);
+    $this->assertEqual($rendered, '<div><h3>Some cats I know</h3><ul><li>Wyatt</li><li>Puck</li></ul></div>');
+  }
+
+}