diff --git a/core/includes/theme.inc b/core/includes/theme.inc
index 2b06429..ecb44d2 100644
--- a/core/includes/theme.inc
+++ b/core/includes/theme.inc
@@ -494,6 +494,9 @@ function _theme($hook, $variables = array()) {
   }
   elseif (!empty($info['render element'])) {
     $variables += array($info['render element'] => array());
+
+    // Declare render variables.
+    $variables['theme_render_variables'][] = $info['render element'];
   }
   // Supply original caller info.
   $variables += array(
@@ -1911,6 +1914,9 @@ function _template_preprocess_default_variables() {
     $variables['db_is_active'] = FALSE;
   }
 
+  $variables['theme_render_variables'][] = 'title_prefix';
+  $variables['theme_render_variables'][] = 'title_suffix';
+
   // Give modules a chance to alter the default template variables.
   \Drupal::moduleHandler()->alter('template_preprocess_default_variables', $variables);
 
diff --git a/core/lib/Drupal/Core/Template/TwigEnvironment.php b/core/lib/Drupal/Core/Template/TwigEnvironment.php
index c671899..bd86df1 100644
--- a/core/lib/Drupal/Core/Template/TwigEnvironment.php
+++ b/core/lib/Drupal/Core/Template/TwigEnvironment.php
@@ -22,6 +22,7 @@
 class TwigEnvironment extends \Twig_Environment {
   protected $cache_object = NULL;
   protected $storage = NULL;
+  protected $dynamic_vars = array();
 
   /**
    * Static cache of template classes.
@@ -126,6 +127,29 @@ public function loadTemplate($name, $index = NULL) {
   }
 
   /**
+   * @todo
+   *
+   * @param array $vars @todo
+   * @param string $name @todo
+   */
+  public function setDynamicVars($vars, $name) {
+    $this->dynamic_vars[$name] = $vars;
+  }
+
+  /**
+   * @todo
+   *
+   * @param  string $name @todo
+   * @return string       @todo
+   */
+  public function getDynamicVars($name) {
+    if (isset($this->dynamic_vars[$name])) {
+      return $this->dynamic_vars[$name];
+    }
+    return NULL;
+  }
+
+  /**
    * Gets the PHP code storage object to use for the compiled Twig files.
    *
    * @return \Drupal\Component\PhpStorage\PhpStorageInterface
diff --git a/core/lib/Drupal/Core/Template/TwigNodeVisitor.php b/core/lib/Drupal/Core/Template/TwigNodeVisitor.php
index a24ee50..10ce0a0 100644
--- a/core/lib/Drupal/Core/Template/TwigNodeVisitor.php
+++ b/core/lib/Drupal/Core/Template/TwigNodeVisitor.php
@@ -19,9 +19,42 @@
 class TwigNodeVisitor implements \Twig_NodeVisitorInterface {
 
   /**
-   * {@inheritdoc}
+   * TRUE when this node is a function getting arguments by reference.
+   *
+   * For example: 'hide' or 'render' are such functions.
+   *
+   * @var bool
+   */
+  protected $isReference = FALSE;
+  protected $dynamic_vars = array();
+
+  /**
+   * Implements Twig_NodeVisitorInterface::enterNode().
    */
   function enterNode(\Twig_NodeInterface $node, \Twig_Environment $env) {
+    if ($node instanceof \Twig_Node_Module) {
+      $filename = $node->getAttribute('filename');
+      $this->dynamic_vars = $env->getDynamicVars($filename);
+    }
+
+   if ($node instanceof \Twig_Node_Expression_Function) {
+      $name = $node->getAttribute('name');
+      $func = $env->getFunction($name);
+
+      // Optimization: Do not support nested functions.
+      if ($this->isReference && $func instanceof \Twig_Function_Function) {
+        $this->isReference = FALSE;
+      }
+      if ($func instanceof TwigReferenceFunction) {
+        // We need to create a TwigReference
+        $this->isReference = TRUE;
+      }
+    }
+    if ($node instanceof \Twig_Node_Print && $this->isReference) {
+       // Our injected render_var needs arguments passed by reference -- in case of render array
+      $this->isReference = TRUE;
+    }
+
     return $node;
   }
 
@@ -40,6 +73,20 @@ function leaveNode(\Twig_NodeInterface $node, \Twig_Environment $env) {
       );
     }
 
+    if ($this->isReference) {
+      if ($node instanceof \Twig_Node_Expression_Name) {
+        $name = $node->getAttribute('name');
+        if (!isset($this->dynamic_vars['render_variables']) || in_array($name, $this->dynamic_vars['render_variables'])) {
+          return new TwigNodeExpressionNameReference($name, $node->getLine());
+        }
+        $this->isReference = FALSE;
+      }
+      elseif ($node instanceof \Twig_Function_Function) {
+        // Do something!
+        $this->isReference = FALSE;
+      }
+    }
+
     return $node;
   }
 
diff --git a/core/themes/engines/twig/twig.engine b/core/themes/engines/twig/twig.engine
index 1595bf8..756c77d 100644
--- a/core/themes/engines/twig/twig.engine
+++ b/core/themes/engines/twig/twig.engine
@@ -45,7 +45,14 @@ function twig_init(Extension $theme) {
  *   The output generated by the template, plus any debug information.
  */
 function twig_render_template($template_file, $variables) {
-  $twig_service = \Drupal::service('twig');
+  $variables['_references'] = array();
+
+  $twig = Drupal::service('twig');
+  $dynamic_vars = array(
+    'render_variables' => $variables['theme_render_variables'],
+  );
+  $twig->setDynamicVars($dynamic_vars, $template_file);
+
   $output = array(
     'debug_prefix'    => '',
     'debug_info'      => '',