.../Drupal/Core/Template/ThemeRegistryNodeVisitor.php   | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/core/lib/Drupal/Core/Template/ThemeRegistryNodeVisitor.php b/core/lib/Drupal/Core/Template/ThemeRegistryNodeVisitor.php
index 6114392..40ae538 100644
--- a/core/lib/Drupal/Core/Template/ThemeRegistryNodeVisitor.php
+++ b/core/lib/Drupal/Core/Template/ThemeRegistryNodeVisitor.php
@@ -130,14 +130,14 @@ protected function getReplacementNode(\Twig_Node_Expression_Constant $node, arra
   /**
    * Returns candidate templates based on the theme registry.
    *
-   * @param string $template_filepath
-   *   The full path relative to the Drupal root for this template.
+   * @param string $template_filename
+   *   The template file name.
    *
    * @return string[]
    *   The candidate templates, including the current template.
    */
-  protected function getCandidateTemplates($template_filepath) {
-    $template_filename = basename($template_filepath);
+  protected function getCandidateTemplates($template_filename) {
+    assert('strpos($template_filename, "/") === FALSE');
     $theme_hook = str_replace('.html.twig', '', strtr($template_filename, '-', '_'));
     $info = $this->themeRegistry->getRuntime()->get($theme_hook);
 
@@ -150,8 +150,8 @@ protected function getCandidateTemplates($template_filepath) {
   /**
    * Returns candidate parent templates based on the theme registry.
    *
-   * @param string $template_filepath
-   *   The full path relative to the Drupal root for this template.
+   * @param string $template_filename
+   *   The template file name.
    * @param string $template_path
    *   The path relative to the Drupal root for the directory that contains this
    *   template.
@@ -159,8 +159,9 @@ protected function getCandidateTemplates($template_filepath) {
    * @return string[]|false
    *   The candidate parent templates, or FALSE when none exist.
    */
-  protected function getCandidateParentTemplates($template_filepath, $template_path) {
-    $candidates = $this->getCandidateTemplates($template_filepath);
+  protected function getCandidateParentTemplates($template_filename, $template_path) {
+    assert('strpos($template_filename, "/") === FALSE');
+    $candidates = $this->getCandidateTemplates($template_filename);
 
     // The candidates include the current template too, so there must be >=2.
     if (count($candidates) < 2) {