diff --git a/core/includes/theme.inc b/core/includes/theme.inc
index a58b59a..b58958a 100644
--- a/core/includes/theme.inc
+++ b/core/includes/theme.inc
@@ -951,30 +951,47 @@ function theme_get_setting($setting_name, $theme = NULL) {
         }
       }
 
+      // A dummy query-string is added to filenames, to gain control over
+      // browser-caching. The string changes on every update or full cache
+      // flush, forcing browsers to load a new copy of the files, as the
+      // URL changed.
+      try {
+        $query_string = \Drupal::state()->get('system.drupal_asset_query_string') ?: '0';
+      }
+      catch(Exception $e) {
+        $query_string = '0';
+      }
+
       // Generate the path to the logo image.
       if ($cache[$theme]->get('features.logo')) {
-        $logo_path = $cache[$theme]->get('logo.path');
         if ($cache[$theme]->get('logo.use_default')) {
-          $cache[$theme]->set('logo.url', file_create_url($theme_object->getPath() . '/logo.png'));
+          if (!file_exists($logo_path = $theme_object->getPath . '/logo.png')) {
+            $logo_path = 'core/misc/druplicon.png';
+          }
         }
-        elseif ($logo_path) {
-          $cache[$theme]->set('logo.url', file_create_url($logo_path));
+        else {
+          $logo_path = $cache[$theme]->get('logo.path');
+        }
+        if ($logo_path) {
+          $query_string_separator = (strpos($logo_path, '?') !== FALSE) ? '&' : '?';
+          $cache[$theme]->set('logo.url', file_create_url($logo_path) . $query_string_separator . $query_string);
         }
       }
 
       // Generate the path to the favicon.
       if ($cache[$theme]->get('features.favicon')) {
-        $favicon_path = $cache[$theme]->get('favicon.path');
         if ($cache[$theme]->get('favicon.use_default')) {
-          if (file_exists($favicon = $theme_object->getPath() . '/favicon.ico')) {
-            $cache[$theme]->set('favicon.url', file_create_url($favicon));
-          }
-          else {
-            $cache[$theme]->set('favicon.url', file_create_url('core/misc/favicon.ico'));
+          if (!file_exists($favicon_path = $theme_object->getPath . '/favicon.ico')) {
+            $favicon_path = 'core/misc/favicon.ico';
           }
         }
-        elseif ($favicon_path) {
-          $cache[$theme]->set('favicon.url', file_create_url($favicon_path));
+        else {
+          $favicon_path = $cache[$theme]->get('favicon.path');
+        }
+        if ($favicon_path) {
+          $query_string_separator = (strpos($favicon_path, '?') !== FALSE) ? '&' : '?';
+          $favicon_url = file_create_url($favicon_path) . $query_string_separator . $query_string;
+          $cache[$theme]->set('favicon.url', $favicon_url);
         }
         else {
           $cache[$theme]->set('features.favicon', FALSE);
diff --git a/core/modules/system/lib/Drupal/system/Tests/System/ThemeTest.php b/core/modules/system/lib/Drupal/system/Tests/System/ThemeTest.php
index 520cb11..175c9cf 100644
--- a/core/modules/system/lib/Drupal/system/Tests/System/ThemeTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/System/ThemeTest.php
@@ -49,31 +49,39 @@ function testThemeSettings() {
     $file_relative = strtr($file->uri, array('public:/' => PublicStream::basePath()));
     $default_theme_path = 'core/themes/stark';
 
+    // Logos and favicons receive a query-string.
+    try {
+      $query_string = \Drupal::state()->get('system.drupal_asset_query_string') ?: '0';
+    }
+    catch(Exception $e) {
+      $query_string = '0';
+    }
+
     $supported_paths = array(
       // Raw stream wrapper URI.
       $file->uri => array(
         'form' => file_uri_target($file->uri),
-        'src' => file_create_url($file->uri),
+        'src' => file_create_url($file->uri) . '?' . $query_string,
       ),
       // Relative path within the public filesystem.
       file_uri_target($file->uri) => array(
         'form' => file_uri_target($file->uri),
-        'src' => file_create_url($file->uri),
+        'src' => file_create_url($file->uri) . '?' . $query_string,
       ),
       // Relative path to a public file.
       $file_relative => array(
         'form' => $file_relative,
-        'src' => file_create_url($file->uri),
+        'src' => file_create_url($file->uri) . '?' . $query_string,
       ),
       // Relative path to an arbitrary file.
       'core/misc/druplicon.png' => array(
         'form' => 'core/misc/druplicon.png',
-        'src' => $GLOBALS['base_url'] . '/' . 'core/misc/druplicon.png',
+        'src' => $GLOBALS['base_url'] . '/' . 'core/misc/druplicon.png' . '?' . $query_string,
       ),
       // Relative path to a file in a theme.
       $default_theme_path . '/logo.png' => array(
         'form' => $default_theme_path . '/logo.png',
-        'src' => $GLOBALS['base_url'] . '/' . $default_theme_path . '/logo.png',
+        'src' => $GLOBALS['base_url'] . '/' . $default_theme_path . '/logo.png' . '?' . $query_string,
       ),
     );
     foreach ($supported_paths as $input => $expected) {
@@ -171,7 +179,7 @@ function testThemeSettings() {
         ':rel' => 'home',
       )
     );
-    $this->assertEqual($elements[0]['src'], file_create_url($uploaded_filename));
+    $this->assertEqual($elements[0]['src'], file_create_url($uploaded_filename) . '?' . $query_string);
   }
 
   /**