diff --git a/core/modules/system/src/Tests/Theme/TwigDebugMarkupTest.php b/core/modules/system/src/Tests/Theme/TwigDebugMarkupTest.php
index efb0818..52b12c3 100644
--- a/core/modules/system/src/Tests/Theme/TwigDebugMarkupTest.php
+++ b/core/modules/system/src/Tests/Theme/TwigDebugMarkupTest.php
@@ -47,7 +47,7 @@ function testTwigDebugMarkup() {
     $build = node_view($node);
     $output = drupal_render($build);
     $this->assertTrue(strpos($output, '<!-- THEME DEBUG -->') !== FALSE, 'Twig debug markup found in theme output when debug is enabled.');
-    $this->assertTrue(strpos($output, "CALL: _theme('node')") !== FALSE, 'Theme call information found.');
+    $this->assertTrue(strpos($output, "THEME HOOK: 'node'") !== FALSE, 'Theme call information found.');
     $this->assertTrue(strpos($output, '* node--1--full' . $extension  . PHP_EOL . '   x node--1' . $extension . PHP_EOL . '   * node--page--full' . $extension . PHP_EOL . '   * node--page' . $extension . PHP_EOL . '   * node--full' . $extension . PHP_EOL . '   * node' . $extension) !== FALSE, 'Suggested template files found in order and node ID specific template shown as current template.');
     $template_filename = $templates['node__1']['path'] . '/' . $templates['node__1']['template'] . $extension;
     $this->assertTrue(strpos($output, "BEGIN OUTPUT from '$template_filename'") !== FALSE, 'Full path to current template file found.');
@@ -65,7 +65,7 @@ function testTwigDebugMarkup() {
     $build = array('#theme' => 'node__foo__bar');
     $build += node_view($node3);
     $output = drupal_render($build);
-    $this->assertTrue(strpos($output, "CALL: _theme('node__foo__bar')") !== FALSE, 'Theme call information found.');
+    $this->assertTrue(strpos($output, "THEME HOOK: 'node__foo__bar'") !== FALSE, 'Theme call information found.');
     $this->assertTrue(strpos($output, '* node--foo--bar' . $extension . PHP_EOL . '   * node--foo' . $extension . PHP_EOL . '   * node--3--full' . $extension . PHP_EOL . '   * node--3' . $extension . PHP_EOL . '   * node--page--full' . $extension . PHP_EOL . '   * node--page' . $extension . PHP_EOL . '   * node--full' . $extension . PHP_EOL . '   x node' . $extension) !== FALSE, 'Suggested template files found in order and base template shown as current template.');
 
     // Disable debug, rebuild the service container, and clear all caches.
diff --git a/core/themes/engines/twig/twig.engine b/core/themes/engines/twig/twig.engine
index e0cfcc2..d09d3b0 100644
--- a/core/themes/engines/twig/twig.engine
+++ b/core/themes/engines/twig/twig.engine
@@ -57,7 +57,7 @@ function twig_render_template($template_file, $variables) {
   );
   if ($twig_service->isDebug()) {
     $output['debug_prefix'] .= "\n\n<!-- THEME DEBUG -->";
-    $output['debug_prefix'] .= "\n<!-- CALL: _theme('{$variables['theme_hook_original']}') -->";
+    $output['debug_prefix'] .= "\n<!-- THEME HOOK: '{$variables['theme_hook_original']}' -->";
     // If there are theme suggestions, reverse the array so more specific
     // suggestions are shown first.
     if (!empty($variables['theme_hook_suggestions'])) {