diff --git a/core/includes/module.inc b/core/includes/module.inc
index b5c0240..935a003 100644
--- a/core/includes/module.inc
+++ b/core/includes/module.inc
@@ -177,7 +177,7 @@ function system_list($type) {
       // Drupal installations, which might have modules installed in different
       // locations in the file system. The ordering here must also be
       // consistent with the one used in module_implements().
-      $result = db_query("SELECT * FROM {system} WHERE (type = 'theme' OR type = 'module') AND status = 1 ORDER BY weight ASC, name ASC");
+      $result = db_query("SELECT * FROM {system} WHERE type IN ('module', 'theme') AND status = 1 ORDER BY weight ASC, name ASC");
       foreach ($result as $record) {
         // Build a list of all enabled modules.
         if ($record->type == 'module') {
diff --git a/core/includes/theme.inc b/core/includes/theme.inc
index 652fab9..fba800a 100644
--- a/core/includes/theme.inc
+++ b/core/includes/theme.inc
@@ -60,6 +60,9 @@ function theme_load($name) {
  *
  * @param $theme
  *   The theme object to return the title for.
+ *
+ * This needs to be a private function to avoid clashing with a possible
+ * theme_menu_title() theme function by Menu or a potential Menu Title module.
  */
 function _theme_menu_title($theme) {
   return check_plain($theme->info['name']);
@@ -72,14 +75,9 @@ function _theme_menu_title($theme) {
  *   Either the name of a theme or a full theme object.
  *
  * @return
- *   Boolean TRUE if the theme is enabled or is the site administration theme;
- *   FALSE otherwise.
+ *   Boolean TRUE if the theme is enabled; FALSE otherwise.
  */
 function drupal_theme_access($theme) {
-  // Early-return for potentially bogus '0', FALSE, or NULL values.
-  if (empty($theme)) {
-    return FALSE;
-  }
   if (is_object($theme)) {
     return !empty($theme->status);
   }
diff --git a/core/modules/block/block.module b/core/modules/block/block.module
index 4f5f0aa..7c60387 100644
--- a/core/modules/block/block.module
+++ b/core/modules/block/block.module
@@ -199,9 +199,14 @@ function block_menu_local_tasks_alter(&$data, $router_item, $root_path) {
     // default theme.
     $themes = list_themes();
     $default_theme = variable_get('theme_default', 'stark');
-    foreach ($data['tabs'][0] as &$tab) {
-      if (isset($tab['#link']['path']) && $tab['#link']['path'] == 'admin/structure/block/list/default') {
-        $tab['#link']['title'] = $themes[$default_theme]->info['name'];
+    foreach ($data['tabs'][0] as $i => &$tab) {
+      if (isset($tab['#link']['path'])) {
+        if ($tab['#link']['path'] == 'admin/structure/block/list/default') {
+          $tab['#link']['title'] = $themes[$default_theme]->info['name'];
+        }
+        elseif ($tab['#link']['path'] == 'admin/structure/block/list/%') {
+          $selected_theme_index = $i;
+        }
       }
     }
 
@@ -214,8 +219,11 @@ function block_menu_local_tasks_alter(&$data, $router_item, $root_path) {
       }
       // If the current page shows the interface for a selected theme, then the
       // menu router item with the %theme argument will expose the selected
-      // theme already; do not duplicate that tab.
+      // theme already; do not duplicate that tab, but ensure it appears in a
+      // consistent order when switching between tabs.
       if ($theme->name === $selected_theme) {
+        $data['tabs'][0][] = $data['tabs'][0][$selected_theme_index];
+        unset($data['tabs'][0][$selected_theme_index]);
         continue;
       }
       $data['tabs'][0][] = array(
diff --git a/core/modules/system/system.admin.inc b/core/modules/system/system.admin.inc
index 0fa4062..c10566d 100644
--- a/core/modules/system/system.admin.inc
+++ b/core/modules/system/system.admin.inc
@@ -363,14 +363,17 @@ function system_theme_default() {
 /**
  * Form builder; display theme configuration for entire site and individual themes.
  *
- * @param $key
- *   A theme name.
+ * @param $theme
+ *   (optional) A theme object.
+ *
  * @return
  *   The form structure.
+ *
  * @ingroup forms
  * @see system_theme_settings_submit()
  */
-function system_theme_settings($form, &$form_state, $key = '') {
+function system_theme_settings($form, &$form_state, $theme = NULL) {
+  $key = !empty($theme) ? $theme->name : '';
   // Default settings are defined in theme_get_setting() in includes/theme.inc
   if ($key) {
     $var = 'theme_' . $key . '_settings';
diff --git a/core/modules/system/system.module b/core/modules/system/system.module
index b6d4608..8c1c5f0 100644
--- a/core/modules/system/system.module
+++ b/core/modules/system/system.module
@@ -693,23 +693,21 @@ function system_menu() {
     'file' => 'system.admin.inc',
     'weight' => 20,
   );
-  // Theme configuration subtabs.
   $items['admin/appearance/settings/global'] = array(
     'title' => 'Global settings',
     'type' => MENU_DEFAULT_LOCAL_TASK,
-    'weight' => -1,
+    'weight' => -10,
+  );
+  $items['admin/appearance/settings/%theme'] = array(
+    'title' => 'Theme settings',
+    'title callback' => '_theme_menu_title',
+    'title arguments' => array(3),
+    'page arguments' => array('system_theme_settings', 3),
+    'access callback' => '_system_themes_access',
+    'access arguments' => array(3),
+    'type' => MENU_LOCAL_TASK,
+    'file' => 'system.admin.inc',
   );
-
-  foreach (list_themes() as $key => $theme) {
-    $items['admin/appearance/settings/' . $theme->name] = array(
-      'title' => $theme->info['name'],
-      'page arguments' => array('system_theme_settings', $theme->name),
-      'type' => MENU_LOCAL_TASK,
-      'access callback' => '_system_themes_access',
-      'access arguments' => array($key),
-      'file' => 'system.admin.inc',
-    );
-  }
 
   // Modules.
   $items['admin/modules'] = array(
@@ -1120,6 +1118,41 @@ function system_menu() {
 }
 
 /**
+ * Implements hook_menu_local_tasks_alter().
+ */
+function system_menu_local_tasks_alter(&$data, $router_item, $root_path) {
+  if ($root_path === 'admin/appearance/settings' || $root_path === 'admin/appearance/settings/%') {
+    // Expand the dynamic %theme argument into a tab for each theme.
+    foreach ($data['tabs'][1] as $i => $tab) {
+      if (isset($tab['#link']['path']) && $tab['#link']['path'] == 'admin/appearance/settings/%') {
+        $selected_theme_index = $i;
+        break;
+      }
+    }
+    $themes = list_themes();
+    $selected_theme = isset($router_item['original_map'][3]) ? $router_item['original_map'][3] : NULL;
+    foreach ($themes as $theme) {
+      // If the current page shows the interface for a selected theme, then the
+      // menu router item with the %theme argument will expose the selected
+      // theme already; do not duplicate that tab, but ensure it appears in a
+      // consistent order when switching between tabs.
+      if ($theme->name === $selected_theme) {
+        $data['tabs'][1][] = $data['tabs'][1][$selected_theme_index];
+        unset($data['tabs'][1][$selected_theme_index]);
+        continue;
+      }
+      $data['tabs'][1][] = array(
+        '#theme' => 'menu_local_task',
+        '#link' => array(
+          'title' => $theme->info['name'],
+          'href' => 'admin/appearance/settings/' . $theme->name,
+        ),
+      );
+    }
+  }
+}
+
+/**
  * Page callback; Execute cron tasks.
  *
  * @see system_cron_access().