diff --git a/core/includes/theme.inc b/core/includes/theme.inc
index cd59f95..68d4716 100644
--- a/core/includes/theme.inc
+++ b/core/includes/theme.inc
@@ -1058,8 +1058,8 @@ function theme($hook, $variables = array()) {
 
   // Provide immutable context for subsequent hooks.
   $context_original = array(
-    'hook' => $hook,
-    'original_hook' => $original_hook,
+    'theme_id' => $hook,
+    'original_theme_id' => $original_hook,
     'suggestions' => $suggestions,
   );
 
@@ -1100,7 +1100,8 @@ function theme($hook, $variables = array()) {
     }
   }
 
-  // Invokes hook_theme_prepare_alter(), hook_theme_prepare_THEME_ID_alter() for enabled modules.
+  // Invokes hook_theme_prepare_alter(), hook_theme_prepare_THEME_ID_alter()
+  // for enabled modules.
   // @todo Add Drupal::themeHandler()->alter() invocations once implemented.
   // @see https://drupal.org/node/2029819
   foreach ($prepare_hooks as $prepare_hook) {
diff --git a/core/modules/system/tests/modules/theme_test/theme_test.module b/core/modules/system/tests/modules/theme_test/theme_test.module
index 43872ad..8e55fc5 100644
--- a/core/modules/system/tests/modules/theme_test/theme_test.module
+++ b/core/modules/system/tests/modules/theme_test/theme_test.module
@@ -194,7 +194,7 @@ function theme_theme_test_prepare_alter_variable($variables) {
  */
 function theme_test_theme_prepare($context) {
   $variables = array();
-  if ($context['#base_theme_id'] == 'theme_test_prepare_variable' || $context['#base_theme_id'] == 'theme_test_prepare_alter_variable') {
+  if ($context['theme_id'] == 'theme_test_prepare_variable' || $context['theme_id'] == 'theme_test_prepare_alter_variable') {
     $variables['element'] = array(
       'variable1' => array(
         '#markup' => '<p>Inserted variable1 via hook_theme_prepare().</p>',
@@ -234,7 +234,7 @@ function theme_test_theme_prepare_theme_test_prepare_alter_variable() {
  * Implements hook_theme_prepare_alter().
  */
 function theme_test_theme_prepare_alter(&$variables, $context) {
-  if ($context['#base_theme_id'] == 'theme_test_prepare_alter_variable') {
+  if ($context['theme_id'] == 'theme_test_prepare_alter_variable') {
     $variables['element']['variable1']['#markup'] = '<p>Inserted variable1 via hook_theme_prepare() was altered by hook_theme_prepare_alter().</p>';
   }
 }
diff --git a/core/modules/system/tests/modules/theme_test/theme_test.routing.yml b/core/modules/system/tests/modules/theme_test/theme_test.routing.yml
index 446f780..53842d4 100644
--- a/core/modules/system/tests/modules/theme_test/theme_test.routing.yml
+++ b/core/modules/system/tests/modules/theme_test/theme_test.routing.yml
@@ -42,28 +42,28 @@ theme_test.request_listener:
   requirements:
     _access: 'TRUE'
 
-suggestion_alter:
+theme_test.suggestion_alter:
   path: '/theme-test/suggestion-alter'
   defaults:
     _content: '\Drupal\theme_test\ThemeTestController::suggestionAlter'
   requirements:
     _permission: 'access content'
 
-suggestion_provided:
+theme_test.suggestion_provided:
   path: '/theme-test/suggestion-provided'
   defaults:
     _content: '\Drupal\theme_test\ThemeTestController::suggestionProvided'
   requirements:
     _permission: 'access content'
 
-specific_suggestion_alter:
+theme_test.specific_suggestion_alter:
   path: '/theme-test/specific-suggestion-alter'
   defaults:
     _content: '\Drupal\theme_test\ThemeTestController::specificSuggestionAlter'
   requirements:
     _permission: 'access content'
 
-function_suggestion_alter:
+theme_test.function_suggestion_alter:
   path: '/theme-test/function-suggestion-alter'
   defaults:
     _content: '\Drupal\theme_test\ThemeTestController::functionSuggestionAlter'
@@ -71,14 +71,14 @@ function_suggestion_alter:
     _permission: 'access content'
 
 theme_test.prepare:
-  pattern: '/theme-test/prepare'
+  path: '/theme-test/prepare'
   defaults:
     _content: '\Drupal\theme_test\ThemeTestController::prepare'
   requirements:
     _permission: 'access content'
 
 theme_test.prepare_alter:
-  pattern: '/theme-test/prepare-alter'
+  path: '/theme-test/prepare-alter'
   defaults:
     _content: '\Drupal\theme_test\ThemeTestController::prepareAlter'
   requirements:
diff --git a/core/modules/system/tests/themes/test_theme/test_theme.theme b/core/modules/system/tests/themes/test_theme/test_theme.theme
index 5f07789..ac559ec 100644
--- a/core/modules/system/tests/themes/test_theme/test_theme.theme
+++ b/core/modules/system/tests/themes/test_theme/test_theme.theme
@@ -75,7 +75,7 @@ function test_theme_theme_test_function_suggestions__module_override($variables)
  */
 function test_theme_theme_prepare($context) {
   $variables = array();
-  if ($context['#base_theme_id'] == 'theme_test_prepare_variable' || $context['#base_theme_id'] == 'theme_test_prepare_alter_variable') {
+  if ($context['theme_id'] == 'theme_test_prepare_variable' || $context['theme_id'] == 'theme_test_prepare_alter_variable') {
     $variables['element'] = array(
       'themeVariable1' => array(
         '#markup' => '<p>Inserted themeVariable1 via theme hook_theme_prepare().</p>',
@@ -115,7 +115,7 @@ function test_theme_theme_prepare_theme_test_prepare_alter_variable() {
  * Implements hook_theme_prepare_alter().
  */
 function test_theme_theme_prepare_alter(&$variables, $context) {
-  if ($context['#base_theme_id'] == 'theme_test_prepare_alter_variable') {
+  if ($context['theme_id'] == 'theme_test_prepare_alter_variable') {
     $variables['element']['themeVariable1']['#markup'] = '<p>Inserted themeVariable1 via theme hook_theme_prepare() was altered by theme hook_theme_prepare_alter().</p>';
   }
 }