diff --git a/core/config/schema/core.data_types.schema.yml b/core/config/schema/core.data_types.schema.yml
index ee8c147..fc534df 100644
--- a/core/config/schema/core.data_types.schema.yml
+++ b/core/config/schema/core.data_types.schema.yml
@@ -101,12 +101,69 @@ action_configuration_default:
   sequence:
     - type: string
 
-theme_settings_default:
+theme_settings:
   type: mapping
   mapping:
-    shortcut_module_link:
-      type: boolean
-      label: 'Shortcut module link'
+    favicon:
+      type: mapping
+      label: 'Shortcut icon settings'
+      mapping:
+        mimetype:
+          type: string
+          label: 'MIME type'
+        path:
+          type: string
+          label: 'Path'
+        url:
+          type: string
+          label: 'URL'
+        use_default:
+          type: boolean
+          label: 'Use the default shortcut icon supplied by the theme'
+    features:
+      type: mapping
+      label: 'Shortcut icon settings'
+      mapping:
+        comment_user_picture:
+          type: boolean
+          label: 'User pictures in comments'
+        comment_user_verification:
+          type: boolean
+          label: 'User verification status in comments'
+        favicon:
+          type: boolean
+          label: 'Shortcut icon'
+        logo:
+          type: boolean
+          label: 'Logo'
+        name:
+          type: boolean
+          label: 'Site name'
+        node_user_picture:
+          type: boolean
+          label: 'User pictures in posts'
+        main_menu:
+          type: boolean
+          label: 'Main menu'
+        secondary_menu:
+          type: boolean
+          label: 'Secondary menu'
+        slogan:
+          type: boolean
+          label: 'Site slogan'
+    logo:
+      type: mapping
+      label: 'Shortcut icon settings'
+      mapping:
+        path:
+          type: string
+          label: 'Logo path'
+        url:
+          type: uri
+          label: 'URL'
+        use_default:
+          type: boolean
+          label: 'Use default'
 
 theme_breakpoints_default:
   type: sequence
diff --git a/core/includes/theme.inc b/core/includes/theme.inc
index c51867e..befa099 100644
--- a/core/includes/theme.inc
+++ b/core/includes/theme.inc
@@ -11,6 +11,7 @@
 use Drupal\Component\Utility\String;
 use Drupal\Component\Utility\UrlHelper;
 use Drupal\Core\Config\Config;
+use Drupal\Core\Config\StorageException;
 use Drupal\Core\Language\Language;
 use Drupal\Core\Extension\Extension;
 use Drupal\Core\Extension\ExtensionNameLengthException;
@@ -861,6 +862,7 @@ function theme_get_setting($setting_name, $theme = NULL) {
       else {
         $theme_keys = array($theme);
       }
+      // Read hard-coded default settings from the theme info files.
       foreach ($theme_keys as $theme_key) {
         if (!empty($themes[$theme_key]->info['settings'])) {
           $cache[$theme]->merge($themes[$theme_key]->info['settings']);
@@ -872,12 +874,17 @@ function theme_get_setting($setting_name, $theme = NULL) {
     $cache[$theme]->merge(\Drupal::config('system.theme.global')->get());
 
     if ($theme) {
-      // Get the saved theme-specific settings from the configuration system.
-      $cache[$theme]->merge(\Drupal::config($theme . '.settings')->get());
+      // Retrieve configured theme-specific settings, if any.
+      try {
+        if ($theme_settings = \Drupal::config($theme . '.settings')->get()) {
+          $cache[$theme]->merge($theme_settings);
+        }
+      }
+      catch (StorageException $e) {
+      }
 
       // If the theme does not support a particular feature, override the global
       // setting and set the value to NULL.
-      //$supports = $cache[$theme]->get('supports');
       if (!empty($theme_object->info['features'])) {
         foreach (_system_default_theme_features() as $feature) {
           if (!in_array($feature, $theme_object->info['features'])) {
diff --git a/core/modules/system/config/schema/system.schema.yml b/core/modules/system/config/schema/system.schema.yml
index 5f8b4d4..91f0605 100644
--- a/core/modules/system/config/schema/system.schema.yml
+++ b/core/modules/system/config/schema/system.schema.yml
@@ -385,66 +385,5 @@ system.mail:
           label: 'Default'
 
 system.theme.global:
-  type: mapping
+  type: theme_settings
   label: 'Theme global settings'
-  mapping:
-    favicon:
-      type: mapping
-      label: 'Shortcut icon settings'
-      mapping:
-        mimetype:
-          type: string
-          label: 'MIME type'
-        path:
-          type: string
-          label: 'Path'
-        url:
-          type: string
-          label: 'URL'
-        use_default:
-          type: boolean
-          label: 'Use the default shortcut icon supplied by the theme'
-    features:
-      type: mapping
-      label: 'Shortcut icon settings'
-      mapping:
-        comment_user_picture:
-          type: boolean
-          label: 'User pictures in comments'
-        comment_user_verification:
-          type: boolean
-          label: 'User verification status in comments'
-        favicon:
-          type: boolean
-          label: 'Shortcut icon'
-        logo:
-          type: boolean
-          label: 'Logo'
-        name:
-          type: boolean
-          label: 'Site name'
-        node_user_picture:
-          type: boolean
-          label: 'User pictures in posts'
-        main_menu:
-          type: boolean
-          label: 'Main menu'
-        secondary_menu:
-          type: boolean
-          label: 'Secondary menu'
-        slogan:
-          type: boolean
-          label: 'Site slogan'
-    logo:
-      type: mapping
-      label: 'Shortcut icon settings'
-      mapping:
-        path:
-          type: string
-          label: 'Logo path'
-        url:
-          type: uri
-          label: 'URL'
-        use_default:
-          type: boolean
-          label: 'Use default'
diff --git a/core/themes/bartik/bartik.info.yml b/core/themes/bartik/bartik.info.yml
index 3e49ffd..bd0bf89 100644
--- a/core/themes/bartik/bartik.info.yml
+++ b/core/themes/bartik/bartik.info.yml
@@ -35,6 +35,6 @@ regions:
   footer_thirdcolumn: 'Footer third column'
   footer_fourthcolumn: 'Footer fourth column'
   footer: Footer
-# @todo D8: Remove once themes have to be installed.
+
 settings:
-  shortcut_module_link: '0'
+  shortcut_module_link: false
diff --git a/core/themes/bartik/config/bartik.settings.yml b/core/themes/bartik/config/bartik.settings.yml
deleted file mode 100644
index 3bb124e..0000000
--- a/core/themes/bartik/config/bartik.settings.yml
+++ /dev/null
@@ -1 +0,0 @@
-shortcut_module_link: false
diff --git a/core/themes/bartik/config/schema/bartik.schema.yml b/core/themes/bartik/config/schema/bartik.schema.yml
index 7788d4f..ef355e3 100644
--- a/core/themes/bartik/config/schema/bartik.schema.yml
+++ b/core/themes/bartik/config/schema/bartik.schema.yml
@@ -1,5 +1,5 @@
 # Schema for the configuration files of the Bartik theme.
 
 bartik.settings:
-  type: theme_settings_default
+  type: theme_settings
   label: 'Bartik settings'
diff --git a/core/themes/seven/config/schema/seven.schema.yml b/core/themes/seven/config/schema/seven.schema.yml
index 13f1384..6d4c86e 100644
--- a/core/themes/seven/config/schema/seven.schema.yml
+++ b/core/themes/seven/config/schema/seven.schema.yml
@@ -1,7 +1,7 @@
 # Schema for the configuration files of the Seven theme.
 
 seven.settings:
-  type: theme_settings_default
+  type: theme_settings
   label: 'Seven settings'
 
 seven.breakpoints:
diff --git a/core/themes/seven/config/seven.settings.yml b/core/themes/seven/config/seven.settings.yml
deleted file mode 100644
index f84652c..0000000
--- a/core/themes/seven/config/seven.settings.yml
+++ /dev/null
@@ -1 +0,0 @@
-shortcut_module_link: true
diff --git a/core/themes/seven/seven.info.yml b/core/themes/seven/seven.info.yml
index 582b498..2140bd9 100644
--- a/core/themes/seven/seven.info.yml
+++ b/core/themes/seven/seven.info.yml
@@ -15,9 +15,6 @@ stylesheets-override:
   - jquery.ui.theme.css
 edit_stylesheets:
   - edit.css
-settings:
-  # @todo D8: Remove once themes have to be installed.
-  shortcut_module_link: '1'
 regions:
   content: Content
   help: Help
@@ -26,3 +23,6 @@ regions:
   sidebar_first: 'First sidebar'
 regions_hidden:
   - sidebar_first
+
+settings:
+  shortcut_module_link: true
diff --git a/core/themes/stark/config/schema/stark.schema.yml b/core/themes/stark/config/schema/stark.schema.yml
index 6e0293e..0331170 100644
--- a/core/themes/stark/config/schema/stark.schema.yml
+++ b/core/themes/stark/config/schema/stark.schema.yml
@@ -1,7 +1,7 @@
 # Schema for the configuration files of the Stark theme.
 
 stark.settings:
-  type: theme_settings_default
+  type: theme_settings
   label: 'Stark settings'
 
 stark.breakpoints:
diff --git a/core/themes/stark/config/stark.settings.yml b/core/themes/stark/config/stark.settings.yml
deleted file mode 100644
index 3bb124e..0000000
--- a/core/themes/stark/config/stark.settings.yml
+++ /dev/null
@@ -1 +0,0 @@
-shortcut_module_link: false