diff --git a/includes/theme.inc b/includes/theme.inc
index bd93af2..1c52b9f 100644
--- a/includes/theme.inc
+++ b/includes/theme.inc
@@ -1201,7 +1201,7 @@ function theme($hook, $variables = array()) {
     if (isset($info['path'])) {
       $template_file = $info['path'] . '/' . $template_file;
     }
-    if (variable_get('theme_debug_output', FALSE)) {
+    if (variable_get('theme_debug', FALSE)) {
       $output = _theme_render_template_debug($render_function, $template_file, $variables, $extension);
     }
     else {
@@ -1532,7 +1532,7 @@ function theme_render_template($template_file, $variables) {
  * Renders a template for any engine.
  *
  * Includes the possibility to get debug output by setting the
- * theme_debug_output variable to TRUE.
+ * theme_debug variable to TRUE.
  *
  * @param string $template_function
  *   The function to call for rendering the template.
diff --git a/modules/simpletest/tests/theme.test b/modules/simpletest/tests/theme.test
index 29c322e..9b2d826 100644
--- a/modules/simpletest/tests/theme.test
+++ b/modules/simpletest/tests/theme.test
@@ -525,7 +525,7 @@ class ThemeDebugMarkupTestCase extends DrupalWebTestCase {
   function testDebugOutput() {
     variable_set('theme_default', 'test_theme');
     // Enable the debug output.
-    variable_set('theme_debug_output', TRUE);
+    variable_set('theme_debug', TRUE);
 
     $registry = theme_get_registry();
     $extension = '.tpl.php';
@@ -558,7 +558,7 @@ class ThemeDebugMarkupTestCase extends DrupalWebTestCase {
     $this->assertTrue(strpos($output, '* node--foo--bar' . $extension . PHP_EOL . '   * node--foo' . $extension . PHP_EOL . '   * node--3' . $extension . PHP_EOL . '   * node--page' . $extension . PHP_EOL . '   x node' . $extension) !== FALSE, 'Suggested template files found in order and base template shown as current template.');
 
     // Disable theme debug.
-    variable_set('theme_debug_output', FALSE);
+    variable_set('theme_debug', FALSE);
 
     $this->drupalGet('node/' . $node->nid);
     $this->assertNoRaw('<!-- THEME DEBUG -->', 'Twig debug markup not found in theme output when debug is disabled.');