diff --git a/core/includes/theme.inc b/core/includes/theme.inc
index 45737c5..19e3bab 100644
--- a/core/includes/theme.inc
+++ b/core/includes/theme.inc
@@ -894,6 +894,7 @@ function drupal_find_base_themes($themes, $key, $used_keys = array()) {
  * process functions for them would incur a noticeable performance penalty.
  *
  * @subsection sub_alternate_suggestions Suggesting Alternate Hooks
+ * @todo Update the below section.
  * There are two special variables that these preprocess and process functions
  * can set: 'theme_hook_suggestion' and 'theme_hook_suggestions'. These will be
  * merged together to form a list of 'suggested' alternate theme hooks to use,
@@ -1031,11 +1032,31 @@ function theme($hook, $variables = array()) {
     'theme_hook_original' => $original_hook,
   );
 
-  // Invoke the variable processors, if any. The processors may specify
-  // alternate suggestions for which hook's template/function to use. If the
-  // hook is a suggestion of a base hook, invoke the variable processors of
-  // the base hook, but retain the suggestion as a high priority suggestion to
-  // be used unless overridden by a variable processor function.
+  // Invoke template suggestion alter hooks.
+  $suggestions = array();
+  $suggestion_hooks = array(
+    'theme_suggestions',
+    'theme_suggestions_' . $original_hook,
+  );
+  // @todo Consider passing $original_hook as last argument.
+  Drupal::moduleHandler()->alter($suggestion_hooks, $suggestions, $variables);
+
+  // Store array of suggestions in variables array.
+  $variables['theme_hook_suggestions'] = $suggestions;
+
+  // Check if each suggestion exists in the theme registry, and if so,
+  // use it instead of the hook that theme() was called with. For example, a
+  // function may call theme('node', ...), but a a module can add
+  // 'node__article' as a suggestion via hook_theme_suggestions_HOOK,
+  // enabling a theme to have an alternate template file for article nodes.
+  foreach (array_reverse($suggestions) as $suggestion) {
+    if (isset($hooks[$suggestion])) {
+      $info = $hooks[$suggestion];
+      break;
+    }
+  }
+
+  // Invoke the variable processors, if any.
   if (isset($info['base hook'])) {
     $base_hook = $info['base hook'];
     $base_hook_info = $hooks[$base_hook];
@@ -1046,14 +1067,15 @@ function theme($hook, $variables = array()) {
         include_once DRUPAL_ROOT . '/' . $include_file;
       }
     }
-    if (isset($base_hook_info['preprocess functions']) || isset($base_hook_info['process functions'])) {
-      $variables['theme_hook_suggestion'] = $hook;
-      $hook = $base_hook;
-      $info = $base_hook_info;
+    // Add preprocess and process functions from the base hook to the $info
+    // array.
+    foreach (array('preprocess functions', 'process functions') as $processor) {
+      if (isset($base_hook_info[$processor])) {
+        $info = array_merge($info, array($processor => $base_hook_info[$processor]));
+      }
     }
   }
   if (isset($info['preprocess functions']) || isset($info['process functions'])) {
-    $variables['theme_hook_suggestions'] = array();
     foreach (array('preprocess functions', 'process functions') as $phase) {
       if (!empty($info[$phase])) {
         foreach ($info[$phase] as $processor_function) {
@@ -1063,31 +1085,6 @@ function theme($hook, $variables = array()) {
         }
       }
     }
-    // If the preprocess/process functions specified hook suggestions, and the
-    // suggestion exists in the theme registry, use it instead of the hook that
-    // theme() was called with. This allows the preprocess/process step to
-    // route to a more specific theme hook. For example, a function may call
-    // theme('node', ...), but a preprocess function can add 'node__article' as
-    // a suggestion, enabling a theme to have an alternate template file for
-    // article nodes. Suggestions are checked in the following order:
-    // - The 'theme_hook_suggestion' variable is checked first. It overrides
-    //   all others.
-    // - The 'theme_hook_suggestions' variable is checked in FILO order, so the
-    //   last suggestion added to the array takes precedence over suggestions
-    //   added earlier.
-    $suggestions = array();
-    if (!empty($variables['theme_hook_suggestions'])) {
-      $suggestions = $variables['theme_hook_suggestions'];
-    }
-    if (!empty($variables['theme_hook_suggestion'])) {
-      $suggestions[] = $variables['theme_hook_suggestion'];
-    }
-    foreach (array_reverse($suggestions) as $suggestion) {
-      if (isset($hooks[$suggestion])) {
-        $info = $hooks[$suggestion];
-        break;
-      }
-    }
   }
 
   // Generate the output using either a function or a template.
@@ -2694,11 +2691,6 @@ function template_preprocess_html(&$variables) {
   foreach ($elements as $name => $element) {
     drupal_add_html_head($element, $name);
   }
-
-  // Populate the page template suggestions.
-  if ($suggestions = theme_get_suggestions(arg(), 'html')) {
-    $variables['theme_hook_suggestions'] = $suggestions;
-  }
 }
 
 /**
@@ -2787,11 +2779,6 @@ function template_preprocess_page(&$variables) {
   if ($node = menu_get_object()) {
     $variables['node'] = $node;
   }
-
-  // Populate the page template suggestions.
-  if ($suggestions = theme_get_suggestions(arg(), 'page')) {
-    $variables['theme_hook_suggestions'] = $suggestions;
-  }
 }
 
 /**
@@ -2851,8 +2838,8 @@ function template_process_html(&$variables) {
 /**
  * Generate an array of suggestions from path arguments.
  *
- * This is typically called for adding to the 'theme_hook_suggestions' or
- * 'attributes' class key variables from within preprocess functions, when
+ * This is typically called for adding to the 'hook_theme_suggestions_HOOK'
+ * or 'attributes' class key variables from within preprocess functions, when
  * wanting to base the additional suggestions on the path of the current page.
  *
  * @param $args
@@ -2867,9 +2854,8 @@ function template_process_html(&$variables) {
  *
  * @return
  *   An array of suggestions, suitable for adding to
- *   $variables['theme_hook_suggestions'] within a preprocess function or to
- *   $variables['attributes']['class'] if the suggestions represent extra CSS
- *   classes.
+ *   hook_theme_suggestions_HOOK_alter() or to $variables['attributes']['class']
+ *   if the suggestions represent extra CSS classes.
  */
 function theme_get_suggestions($args, $base, $delimiter = '__') {
 
@@ -3015,12 +3001,6 @@ function template_preprocess_maintenance_page(&$variables) {
     $variables['attributes']['class'][] = 'one-sidebar';
     $variables['attributes']['class'][] = 'sidebar-' . $variables['layout'];
   }
-
-  // Dead databases will show error messages so supplying this template will
-  // allow themers to override the page and the content completely.
-  if (isset($variables['db_is_active']) && !$variables['db_is_active']) {
-    $variables['theme_hook_suggestion'] = 'maintenance_page__offline';
-  }
 }
 
 /**
@@ -3062,7 +3042,6 @@ function template_preprocess_region(&$variables) {
 
   $variables['attributes']['class'][] = 'region';
   $variables['attributes']['class'][] = drupal_html_class('region-' . $variables['region']);
-  $variables['theme_hook_suggestions'][] = 'region__' . $variables['region'];
 }
 
 /**
diff --git a/core/modules/block/block.module b/core/modules/block/block.module
index ca13d32..e4811d4 100644
--- a/core/modules/block/block.module
+++ b/core/modules/block/block.module
@@ -505,6 +505,35 @@ function block_rebuild() {
 }
 
 /**
+ * Implements hook_theme_suggestions_HOOK_alter().
+ */
+function block_theme_suggestions_block_alter(&$suggestions, $variables) {
+  $suggestions[] = 'block__' . $variables['elements']['#configuration']['module'];
+  // Hyphens (-) and underscores (_) play a special role in theme suggestions.
+  // Theme suggestions should only contain underscores, because within
+  // drupal_find_theme_templates(), underscores are converted to hyphens to
+  // match template file names, and then converted back to underscores to match
+  // pre-processing and other function names. So if your theme suggestion
+  // contains a hyphen, it will end up as an underscore after this conversion,
+  // and your function names won't be recognized. So, we need to convert
+  // hyphens to underscores in block deltas for the theme suggestions.
+
+  // We can safely explode on : because we know the Block plugin type manager
+  // enforces that delimiter for all derivatives.
+  $parts = explode(':', $variables['elements']['#plugin_id']);
+  $suggestion = 'block';
+  while ($part = array_shift($parts)) {
+    $suggestions[] = $suggestion .= '__' . strtr($part, '-', '_');
+  }
+
+  if ($id = $variables['elements']['#block']->id()) {
+    $config_id = explode('.', $id);
+    $machine_name = array_pop($config_id);
+    $suggestions[] = 'block__' . $machine_name;
+  }
+}
+
+/**
  * Prepares variables for block templates.
  *
  * Default template: block.html.twig.
@@ -547,29 +576,11 @@ function template_preprocess_block(&$variables) {
   // Add default class for block content.
   $variables['content_attributes']['class'][] = 'content';
 
-  $variables['theme_hook_suggestions'][] = 'block__' . $variables['configuration']['module'];
-  // Hyphens (-) and underscores (_) play a special role in theme suggestions.
-  // Theme suggestions should only contain underscores, because within
-  // drupal_find_theme_templates(), underscores are converted to hyphens to
-  // match template file names, and then converted back to underscores to match
-  // pre-processing and other function names. So if your theme suggestion
-  // contains a hyphen, it will end up as an underscore after this conversion,
-  // and your function names won't be recognized. So, we need to convert
-  // hyphens to underscores in block deltas for the theme suggestions.
-
-  // We can safely explode on : because we know the Block plugin type manager
-  // enforces that delimiter for all derivatives.
-  $parts = explode(':', $variables['plugin_id']);
-  $suggestion = 'block';
-  while ($part = array_shift($parts)) {
-    $variables['theme_hook_suggestions'][] = $suggestion .= '__' . strtr($part, '-', '_');
-  }
   // Create a valid HTML ID and make sure it is unique.
   if ($id = $variables['elements']['#block']->id()) {
     $config_id = explode('.', $id);
     $machine_name = array_pop($config_id);
     $variables['attributes']['id'] = drupal_html_id('block-' . $machine_name);
-    $variables['theme_hook_suggestions'][] = 'block__' . $machine_name;
   }
 }
 
diff --git a/core/modules/block/lib/Drupal/block/Tests/BlockTemplateSuggestionsUnitTest.php b/core/modules/block/lib/Drupal/block/Tests/BlockTemplateSuggestionsUnitTest.php
index 51630ba..bc4ab59 100644
--- a/core/modules/block/lib/Drupal/block/Tests/BlockTemplateSuggestionsUnitTest.php
+++ b/core/modules/block/lib/Drupal/block/Tests/BlockTemplateSuggestionsUnitTest.php
@@ -10,7 +10,7 @@
 use Drupal\simpletest\WebTestBase;
 
 /**
- * Unit tests for template_preprocess_block().
+ * Unit tests for block_theme_suggestions_block_alter().
  */
 class BlockTemplateSuggestionsUnitTest extends WebTestBase {
 
@@ -24,13 +24,13 @@ class BlockTemplateSuggestionsUnitTest extends WebTestBase {
   public static function getInfo() {
     return array(
       'name' => 'Block template suggestions',
-      'description' => 'Test the template_preprocess_block() function.',
+      'description' => 'Test the block_theme_suggestions_block_alter() function.',
       'group' => 'Block',
     );
   }
 
   /**
-   * Test if template_preprocess_block() handles the suggestions right.
+   * Tests template suggestions from block_theme_suggestions_block_alter().
    */
   function testBlockThemeHookSuggestions() {
     // Define a block with a derivative to be preprocessed, which includes both
@@ -43,16 +43,15 @@ function testBlockThemeHookSuggestions() {
       'id' => config('system.theme')->get('default') . '.machinename',
     ));
 
+    // @todo Cast to array in suggestions alter hook signature?
+    $suggestions = array();
     $variables = array();
     $variables['elements']['#block'] = $block;
     $variables['elements']['#configuration'] = $block->getPlugin()->getConfig();
     $variables['elements']['#plugin_id'] = $block->get('plugin');
     $variables['elements']['content'] = array();
-    // Test adding a class to the block content.
-    $variables['content_attributes']['class'][] = 'test-class';
-    template_preprocess_block($variables);
-    $this->assertEqual($variables['theme_hook_suggestions'], array('block__system', 'block__system_menu_block', 'block__system_menu_block__menu_admin', 'block__machinename'));
-    $this->assertEqual($variables['content_attributes']['class'], array('test-class', 'content'), 'Default .content class added to block content_attributes');
+    block_theme_suggestions_block_alter($suggestions, $variables);
+    $this->assertEqual($suggestions, array('block__system', 'block__system_menu_block', 'block__system_menu_block__menu_admin', 'block__machinename'));
   }
 
 }
diff --git a/core/modules/field/field.module b/core/modules/field/field.module
index 403ace2..c20f9cf 100644
--- a/core/modules/field/field.module
+++ b/core/modules/field/field.module
@@ -952,6 +952,20 @@ function field_page_build(&$page) {
 }
 
 /**
+ * Implements hook_theme_suggestions_HOOK_alter().
+ */
+function field_theme_suggestions_field_alter(&$suggestions, $variables) {
+  $element = $variables['element'];
+
+  $suggestions = array_merge($suggestions, array(
+    'field__' . $element['#field_type'],
+    'field__' . $element['#field_name'],
+    'field__' . $element['#bundle'],
+    'field__' . $element['#field_name'] . '__' . $element['#bundle'],
+  ));
+}
+
+/**
  * Prepares variables for field templates.
  *
  * Default template: field.html.twig.
@@ -1004,14 +1018,6 @@ function template_preprocess_field(&$variables, $hook) {
   if ($element['#label_display'] == 'inline') {
     $variables['attributes']['class'][] = 'clearfix';
   }
-
-  // Add specific suggestions that can override the default implementation.
-  $variables['theme_hook_suggestions'] = array(
-    'field__' . $element['#field_type'],
-    'field__' . $element['#field_name'],
-    'field__' . $element['#bundle'],
-    'field__' . $element['#field_name'] . '__' . $element['#bundle'],
-  );
 }
 
 /**
diff --git a/core/modules/forum/forum.module b/core/modules/forum/forum.module
index c06edde..ba405df 100644
--- a/core/modules/forum/forum.module
+++ b/core/modules/forum/forum.module
@@ -962,6 +962,28 @@ function forum_preprocess_block(&$variables) {
 }
 
 /**
+ * Implements hook_theme_suggestions_HOOK_alter().
+ */
+function forum_theme_suggestions_forums_alter(&$suggestions, $variables) {
+  // Provide separate template suggestions based on what's being output. Topic
+  // ID is also accounted for. Check both variables to be safe then the inverse.
+  // Forums with topic IDs take precedence.
+  if ($variables['forums'] && !$variables['topics']) {
+    $suggestions[] = 'forums__containers';
+    $suggestions[] = 'forums__' . $variables['tid'];
+    $suggestions[] = 'forums__containers__' . $variables['tid'];
+  }
+  elseif (!$variables['forums'] && $variables['topics']) {
+    $suggestions[] = 'forums__topics';
+    $suggestions[] = 'forums__' . $variables['tid'];
+    $suggestions[] = 'forums__topics__' . $variables['tid'];
+  }
+  else {
+    $suggestions[] = 'forums__' . $variables['tid'];
+  }
+}
+
+/**
  * Prepares variables for forums templates.
  *
  * Default template: forums.html.twig.
@@ -1007,23 +1029,6 @@ function template_preprocess_forums(&$variables) {
     else {
       $variables['topics'] = array();
     }
-
-    // Provide separate template suggestions based on what's being output. Topic id is also accounted for.
-    // Check both variables to be safe then the inverse. Forums with topic ID's take precedence.
-    if ($variables['forums'] && !$variables['topics']) {
-      $variables['theme_hook_suggestions'][] = 'forums__containers';
-      $variables['theme_hook_suggestions'][] = 'forums__' . $variables['tid'];
-      $variables['theme_hook_suggestions'][] = 'forums__containers__' . $variables['tid'];
-    }
-    elseif (!$variables['forums'] && $variables['topics']) {
-      $variables['theme_hook_suggestions'][] = 'forums__topics';
-      $variables['theme_hook_suggestions'][] = 'forums__' . $variables['tid'];
-      $variables['theme_hook_suggestions'][] = 'forums__topics__' . $variables['tid'];
-    }
-    else {
-      $variables['theme_hook_suggestions'][] = 'forums__' . $variables['tid'];
-    }
-
   }
   else {
     $variables['forums'] = array();
diff --git a/core/modules/node/node.module b/core/modules/node/node.module
index fbdf07d..71a1435 100644
--- a/core/modules/node/node.module
+++ b/core/modules/node/node.module
@@ -1020,6 +1020,18 @@ function node_preprocess_block(&$variables) {
 }
 
 /**
+ * Implements hook_theme_suggestions_HOOK_alter().
+ */
+function node_theme_suggestions_node_alter(&$suggestions, $variables) {
+  $node = $variables['elements']['#node'];
+
+  $suggestions = array_merge($suggestions, array(
+    'node__' . $node->type,
+    'node__' . $node->nid,
+  ));
+}
+
+/**
  * Prepares variables for node templates.
  *
  * Default template: node.html.twig.
@@ -1107,10 +1119,6 @@ function template_preprocess_node(&$variables) {
     $variables['attributes']['class'][] = 'preview';
   }
 
-  // Clean up name so there are no underscores.
-  $variables['theme_hook_suggestions'][] = 'node__' . $node->type;
-  $variables['theme_hook_suggestions'][] = 'node__' . $node->nid;
-
   $variables['content_attributes']['class'][] = 'content';
 }
 
diff --git a/core/modules/search/search.pages.inc b/core/modules/search/search.pages.inc
index 646028a..fc3705d 100644
--- a/core/modules/search/search.pages.inc
+++ b/core/modules/search/search.pages.inc
@@ -75,6 +75,13 @@ function search_view($module = NULL, $keys = '') {
 }
 
 /**
+ * Implements hook_theme_suggestions_HOOK_alter().
+ */
+function search_theme_suggestions_search_results_alter(&$suggestions, $variables) {
+  $suggestions[] = 'search_results__' . $variables['module'];
+}
+
+/**
  * Prepares variables for search results templates.
  *
  * Default template: search-results.html.twig.
@@ -104,7 +111,13 @@ function template_preprocess_search_results(&$variables) {
   // @todo Revisit where this help text is added, see also
   //   http://drupal.org/node/1918856.
   $variables['help'] = search_help('search#noresults', drupal_help_arg());
-  $variables['theme_hook_suggestions'][] = 'search_results__' . $variables['module'];
+}
+
+/**
+ * Implements hook_theme_suggestions_HOOK_alter().
+ */
+function search_theme_suggestions_search_result_alter(&$suggestions, $variables) {
+  $suggestions[] = 'search_result__' . $variables['module'];
 }
 
 /**
@@ -153,7 +166,6 @@ function template_preprocess_search_result(&$variables) {
   // Provide separated and grouped meta information..
   $variables['info_split'] = $info;
   $variables['info'] = implode(' - ', $info);
-  $variables['theme_hook_suggestions'][] = 'search_result__' . $variables['module'];
 }
 
 /**
diff --git a/core/modules/system/system.module b/core/modules/system/system.module
index 125f807..f004902 100644
--- a/core/modules/system/system.module
+++ b/core/modules/system/system.module
@@ -1046,6 +1046,40 @@ function system_menu() {
 }
 
 /**
+ * Implements hook_theme_suggestions_HOOK_alter().
+ */
+function system_theme_suggestions_html_alter(&$suggestions, $variables) {
+  $suggestions = array_merge($suggestions, theme_get_suggestions(arg(), 'html'));
+}
+
+/**
+ * Implements hook_theme_suggestions_HOOK_alter().
+ */
+function system_theme_suggestions_page_alter(&$suggestions, $variables) {
+  $suggestions = array_merge($suggestions, theme_get_suggestions(arg(), 'page'));
+}
+
+/**
+ * Implements hook_theme_suggestions_HOOK_alter().
+ */
+function system_theme_suggestions_maintenance_page_alter(&$suggestions, $variables) {
+  // Dead databases will show error messages so supplying this template will
+  // allow themers to override the page and the content completely.
+  if (defined('MAINTENANCE_MODE')) {
+    $suggestions[] = 'maintenance_page__offline';
+  }
+}
+
+/**
+ * Implements hook_theme_suggestions_HOOK_alter().
+ */
+function system_theme_suggestions_region_alter(&$suggestions, $variables) {
+  if (!empty($variables['elements']['#region'])) {
+    $suggestions[] = 'region__' . $variables['elements']['#region'];
+  }
+}
+
+/**
  * Proxies to the plugin class' form method.
  *
  * @todo This needs more explanation, an @see or two, and parameter
diff --git a/core/modules/taxonomy/taxonomy.module b/core/modules/taxonomy/taxonomy.module
index b2c6b83..88c9eae 100644
--- a/core/modules/taxonomy/taxonomy.module
+++ b/core/modules/taxonomy/taxonomy.module
@@ -450,6 +450,16 @@ function taxonomy_term_view_multiple(array $terms, $view_mode = 'full', $langcod
 }
 
 /**
+ * Implements hook_theme_suggestions_HOOK_alter().
+ */
+function taxonomy_theme_suggestions_taxonomy_term_alter(&$suggestions, $variables) {
+  $term = $variables['elements']['#term'];
+
+  $suggestions[] = 'taxonomy_term__' . $term->bundle();
+  $suggestions[] = 'taxonomy_term__' . $term->id();
+}
+
+/**
  * Prepares variables for taxonomy term templates.
  *
  * Default template: taxonomy-term.html.twig.
@@ -490,9 +500,6 @@ function template_preprocess_taxonomy_term(&$variables) {
   $variables['attributes']['class'][] = 'taxonomy-term';
   $vocabulary_name_css = str_replace('_', '-', $term->bundle());
   $variables['attributes']['class'][] = 'vocabulary-' . $vocabulary_name_css;
-
-  $variables['theme_hook_suggestions'][] = 'taxonomy_term__' . $term->bundle();
-  $variables['theme_hook_suggestions'][] = 'taxonomy_term__' . $term->id();
 }
 
 /**
diff --git a/core/modules/views/views.module b/core/modules/views/views.module
index c7077e9..e0da079 100644
--- a/core/modules/views/views.module
+++ b/core/modules/views/views.module
@@ -238,17 +238,13 @@ function views_plugin_list() {
 function views_preprocess_node(&$vars) {
   Drupal::moduleHandler()->loadInclude('node', 'views.inc');
   // The 'view' attribute of the node is added in views_preprocess_node()
+  // @todo The comment above doesn't make any sense to me - it's saying the
+  //   attribute is added in *this* function?
   if (!empty($vars['node']->view) && $vars['node']->view->storage->id()) {
-    $vars['view'] = $vars['node']->view;
-    $vars['theme_hook_suggestions'][] = 'node__view__' . $vars['node']->view->storage->id();
-    if (!empty($vars['node']->view->current_display)) {
-      $vars['theme_hook_suggestions'][] = 'node__view__' . $vars['node']->view->storage->id() . '__' . $vars['node']->view->current_display;
-
-      // If a node is being rendered in a view, and the view does not have a path,
-      // prevent drupal from accidentally setting the $page variable:
-      if ($vars['page'] && $vars['view_mode'] == 'full' && !$vars['view']->display_handler->hasPath()) {
-        $vars['page'] = FALSE;
-      }
+    // If a node is being rendered in a view, and the view does not have a path,
+    // prevent drupal from accidentally setting the $page variable:
+    if ($vars['page'] && $vars['view_mode'] == 'full' && !$vars['view']->display_handler->hasPath()) {
+      $vars['page'] = FALSE;
     }
   }
 
@@ -259,16 +255,40 @@ function views_preprocess_node(&$vars) {
 }
 
 /**
+ * Implements hook_theme_suggestions_HOOK_alter().
+ */
+function views_theme_suggestions_node_alter(&$suggestions, $variables) {
+  if (!empty($variables['node']->view) && $variables['node']->view->storage->id()) {
+    $variables['view'] = $variables['node']->view;
+    $suggestions[] = 'node__view__' . $variables['node']->view->storage->id();
+    if (!empty($variables['node']->view->current_display)) {
+      $suggestions[] = 'node__view__' . $variables['node']->view->storage->id() . '__' . $variables['node']->view->current_display;
+    }
+  }
+}
+
+/**
  * A theme preprocess function to automatically allow view-based node
  * templates if called from a view.
  */
 function views_preprocess_comment(&$vars) {
   // The 'view' attribute of the node is added in template_preprocess_views_view_row_comment()
+  // @todo I can't find the function mentioned in the above comment.
   if (!empty($vars['comment']->view) && $vars['comment']->view->storage->id()) {
     $vars['view'] = &$vars['comment']->view;
-    $vars['theme_hook_suggestions'][] = 'comment__view__' . $vars['comment']->view->storage->id();
-    if (!empty($vars['node']->view->current_display)) {
-      $vars['theme_hook_suggestions'][] = 'comment__view__' . $vars['comment']->view->storage->id() . '__' . $vars['comment']->view->current_display;
+  }
+}
+
+/**
+ * Implements hook_theme_suggestions_HOOK_alter().
+ */
+function views_theme_suggestions_comment_alter(&$suggestions, $variables) {
+  if (!empty($variables['comment']->view) && $variables['comment']->view->storage->id()) {
+    $suggestions[] = 'comment__view__' . $variables['comment']->view->storage->id();
+    // @todo Shouldn't the below be checking $variables['comment'] instead of
+    //   $variables['node']?
+    if (!empty($variables['node']->view->current_display)) {
+      $suggestions[] = 'comment__view__' . $variables['comment']->view->storage->id() . '__' . $variables['comment']->view->current_display;
     }
   }
 }
diff --git a/core/modules/views_ui/views_ui.theme.inc b/core/modules/views_ui/views_ui.theme.inc
index 8e503fc..48eb6d1 100644
--- a/core/modules/views_ui/views_ui.theme.inc
+++ b/core/modules/views_ui/views_ui.theme.inc
@@ -450,7 +450,13 @@ function template_preprocess_views_ui_view_preview_section(&$vars) {
     );
     $vars['links'] = drupal_render($build);
   }
-  $vars['theme_hook_suggestions'][] = 'views_ui_view_preview_section__' . $vars['section'];
+}
+
+/**
+ * Implements hook_theme_suggestions_HOOK_alter().
+ */
+function views_ui_theme_suggestions_views_ui_view_preview_section_alter(&$suggestions, $variables) {
+  $suggestions[] = 'views_ui_view_preview_section__' . $variables['section'];
 }
 
 /**