diff --git a/core/lib/Drupal/Core/Theme/ThemeManager.php b/core/lib/Drupal/Core/Theme/ThemeManager.php
index 6850fcb..d6624cc 100644
--- a/core/lib/Drupal/Core/Theme/ThemeManager.php
+++ b/core/lib/Drupal/Core/Theme/ThemeManager.php
@@ -286,6 +286,20 @@ protected function theme($hook, $variables = array()) {
           include_once $this->root . '/' . $include_file;
         }
       }
+
+      // If base hook has variables defined we want to merge them so they don't
+      // have to be set manually when base hook is defined.
+      if (!empty($base_hook_info['variables'])) {
+        $variables['variables'] = array_merge($base_hook_info['variables'], $variables['variables']);
+      }
+
+      // If render element haven't been defined for current element try to get
+      // it from the base hook.
+      if (empty($info['render element']) && !empty($base_hook_info['render element'])) {
+        $info['render element'] = $base_hook_info['render element'];
+        $variables += array($info['render element'] => array());
+      }
+
       // Replace the preprocess functions with those from the base hook.
       if (isset($base_hook_info['preprocess functions'])) {
         // Set a variable for the 'theme_hook_suggestion'. This is used to