diff --git a/core/includes/theme.inc b/core/includes/theme.inc
index 4c0e580..5bb97ca 100644
--- a/core/includes/theme.inc
+++ b/core/includes/theme.inc
@@ -1445,32 +1445,48 @@ 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.
+      $query_string = state()->get('system.css_js_query_string') ?: '0';
+
       // Generate the path to the logo image.
       if ($cache[$theme]['toggle_logo']) {
+        $logo_path = '';
         if ($cache[$theme]['default_logo']) {
-          $cache[$theme]['logo'] = file_create_url(dirname($theme_object->filename) . '/logo.png');
+          $logo_path = file_create_url(dirname($theme_object->filename) . '/logo.png');
         }
         elseif ($cache[$theme]['logo_path']) {
-          $cache[$theme]['logo'] = file_create_url($cache[$theme]['logo_path']);
+          $logo_path = file_create_url($cache[$theme]['logo_path']);
+        }
+        if (!empty($logo_path)) {
+          $query_string_separator = (strpos($logo_path, '?') !== FALSE) ? '&' : '?';
+          $cache[$theme]['logo'] = $logo_path . $query_string_separator . $query_string;
         }
       }
 
       // Generate the path to the favicon.
       if ($cache[$theme]['toggle_favicon']) {
+        $favicon_path = '';
         if ($cache[$theme]['default_favicon']) {
           if (file_exists($favicon = dirname($theme_object->filename) . '/favicon.ico')) {
-            $cache[$theme]['favicon'] = file_create_url($favicon);
+            $favicon_path = file_create_url($favicon);
           }
           else {
-            $cache[$theme]['favicon'] = file_create_url('core/misc/favicon.ico');
+            $favicon_path = file_create_url('core/misc/favicon.ico');
           }
         }
         elseif ($cache[$theme]['favicon_path']) {
-          $cache[$theme]['favicon'] = file_create_url($cache[$theme]['favicon_path']);
+          $favicon_path = file_create_url($cache[$theme]['favicon_path']);
         }
         else {
           $cache[$theme]['toggle_favicon'] = FALSE;
         }
+        if (!empty($favicon_path)) {
+          $query_string_separator = (strpos($favicon_path, '?') !== FALSE) ? '&' : '?';
+          $cache[$theme]['favicon'] = $favicon_path . $query_string_separator . $query_string;
+        }
       }
     }
   }
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 f636849..91f7cad 100644
--- a/core/modules/system/lib/Drupal/system/Tests/System/ThemeTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/System/ThemeTest.php
@@ -48,31 +48,34 @@ function testThemeSettings() {
     $file_relative = strtr($file->uri, array('public:/' => variable_get('file_public_path', conf_path() . '/files')));
     $default_theme_path = 'core/themes/stark';
 
+    // Logo's and favicons receive a query string.
+    $query_string = variable_get('css_js_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) {
@@ -164,7 +167,7 @@ function testThemeSettings() {
 
     $this->drupalGet('');
     $elements = $this->xpath('//*[@id=:id]/img', array(':id' => 'logo'));
-    $this->assertEqual($elements[0]['src'], file_create_url($uploaded_filename));
+    $this->assertEqual($elements[0]['src'], file_create_url($uploaded_filename) . '?' . $query_string);
   }
 
   /**