diff -u b/core/includes/theme.inc b/core/includes/theme.inc
--- b/core/includes/theme.inc
+++ b/core/includes/theme.inc
@@ -1290,7 +1290,6 @@
 
 function theme_get_setting($setting_name, $theme = NULL) {
   $cache = &drupal_static(__FUNCTION__, array());
-  $global_config = config('system.theme');
 
   // If no key is given, use the current theme if we can determine it.
   if (!isset($theme)) {
@@ -1299,7 +1298,23 @@
 
   if (empty($cache[$theme])) {
     // Set the default values for each global setting.
-    $cache[$theme] = theme_config_convert_newold($global_config->get());
+    $default_config = array(
+      'favicon'  => array('use_default' => 1),
+      'features' => array(
+        'comment_user_picture' => 1,
+        'comment_user_verification' => 1,
+        'favicon' => 1,
+        'logo' => 1,
+        'name' => 1,
+        'node_user_picture' => 1,
+        'main_menu' => 1,
+        'secondary_menu' => 1,
+        'slogan' => 1,
+      ),
+      'logo'     => array('use_default' => 1),
+    );
+    $default_config += config('system.theme')->get();
+    $cache[$theme] = theme_config_convert_newold($default_config);
 
     // Get the values for the theme-specific settings from the .info files of
     // the theme and all its base themes.
@@ -1326,9 +1341,8 @@
 
       // If the theme does not support a particular feature, override the global
       // setting and set the value to NULL.
-      $features = $global_config->get('features');
-      if (!empty($features) and !empty($theme_object->info['features'])) {
-        foreach ($features as $feature) {
+      if (!empty($theme_object->info['features'])) {
+        foreach ($default_config['features'] as $feature) {
           if (!in_array($feature, $theme_object->info['features'])) {
             $cache[$theme]['toggle_' . $feature] = NULL;
           }
@@ -1382,25 +1396,31 @@
   $new_config = array();
 
   foreach ($old_config as $key => $value) {
-    if ($key == 'default_logo' && !empty($value)) {
-      $new_config['logo']['use_default'] = (bool) $value;
+    if ($key == 'logo') {
+      $new_config['logo']['url'] = $value;
     }
-    else if ($key == 'logo_path' && !empty($value)) {
+    else if ($key == 'default_logo') {
+      $new_config['logo']['use_default'] = $value;
+    }
+    else if ($key == 'logo_path') {
       $new_config['logo']['path'] = $value;
     }
-    else if ($key == 'default_favicon' && !empty($value)) {
-      $new_config['favicon']['use_default'] = (bool) $value;
+    else if ($key == 'favicon') {
+      $new_config['favicon']['url'] = $value;
+    }
+    else if ($key == 'default_favicon') {
+      $new_config['favicon']['use_default'] = $value;
     }
-    else if ($key == 'favicon_path' && !empty($value)) {
+    else if ($key == 'favicon_path') {
       $new_config['favicon']['path'] = $value;
     }
-    else if ($key == 'favicon_mimetype' && !empty($value)) {
+    else if ($key == 'favicon_mimetype') {
       $new_config['favicon']['mimetype'] = $value;
     }
-    else if (substr($key, 0, 7) == 'toggle_' && !empty($value)) {
+    else if (substr($key, 0, 7) == 'toggle_') {
       $new_config['features'][substr($key, 7)] = (bool) $value;
     }
-    else if (!empty($value)) {
+    else if (!in_array($key, array('theme'))) {
       $new_config[$key] = $value;
     }
   }
@@ -1423,6 +1443,7 @@
 
   foreach ($new_config as $key => $value) {
     if (in_array($key, array('logo', 'favicon'))) {
+
       if (isset($value['use_default'])) {
         $old_config['default_' . $key] = $value['use_default'];
       }
@@ -1431,6 +1452,10 @@
         $old_config[$key . '_path'] = $value['path'];
       }
 
+      if (isset($value['url'])) {
+        $old_config[$key] = $value['url'];
+      }
+
       if ($key == 'favicon' && isset($value['mimetype'])) {
         $old_config['favicon_mimetype'] = $value['mimetype'];
       }
@@ -1483,9 +1508,6 @@
       ->condition('type', 'theme')
       ->condition('name', $key)
       ->execute();
-
-    // Install default configuration of the theme.
-    config_install_default_config('theme', $key);
   }
 
   list_themes(TRUE);
diff -u b/core/modules/system/config/system.theme.yml b/core/modules/system/config/system.theme.yml
--- b/core/modules/system/config/system.theme.yml
+++ b/core/modules/system/config/system.theme.yml
@@ -1,6 +1,7 @@
 favicon:
     mimetype: image/vnd.microsoft.icon
     path: ''
+    url: ''
     use_default: '1'
 features:
     comment_user_picture: '1'
@@ -16,2 +17,3 @@
     path: ''
+    url: ''
     use_default: '1'
diff -u b/core/modules/system/system.install b/core/modules/system/system.install
--- b/core/modules/system/system.install
+++ b/core/modules/system/system.install
@@ -2004,11 +2004,11 @@
   $variables = array('theme_settings' => 'system.theme');
   $themes = list_themes();
   foreach ($themes as $theme) {
-    $variables['theme_' . $theme->name . '_settings'] = $theme->name . '_settings';
+    $variables['theme_' . $theme->name . '_settings'] = $theme->name . '.settings';
   }
 
   foreach ($variables as $old_key => $new_key) {
-    $config = theme_config_convert_oldnew(variable_get($old_key));
+    $config = theme_config_convert_oldnew(variable_get($old_key, array()));
     $new_config = config($new_key);
     foreach ($config as $key => $value) {
       $new_config->set($key, $value);