diff --git a/core/lib/Drupal/Core/Utility/UnroutedUrlAssembler.php b/core/lib/Drupal/Core/Utility/UnroutedUrlAssembler.php
index c0ce73b..972d930 100644
--- a/core/lib/Drupal/Core/Utility/UnroutedUrlAssembler.php
+++ b/core/lib/Drupal/Core/Utility/UnroutedUrlAssembler.php
@@ -155,13 +155,24 @@ protected function buildLocalUrl($uri, array $options = []) {
    *   The options to merge in the defaults.
    */
   protected function addOptionDefaults(array &$options) {
+    $request = $this->requestStack->getCurrentRequest();
+    $current_base_path = $request->getBasePath() . '/';
+    $current_script_path = '';
+    $base_path_with_script = $request->getBaseUrl();
+    if (!empty($base_path_with_script)) {
+      $script_name = $request->getScriptName();
+      if (strpos($base_path_with_script, $script_name) !== FALSE) {
+        $current_script_path = ltrim(substr($script_name, strlen($current_base_path)), '/') . '/';
+      }
+    }
+
     // Merge in defaults.
     $options += [
       'fragment' => '',
       'query' => [],
       'absolute' => FALSE,
       'prefix' => '',
-      'script' => '',
+      'script' => $current_script_path,
     ];
 
     if (isset($options['fragment']) && $options['fragment'] !== '') {
diff --git a/core/modules/image/src/Entity/ImageStyle.php b/core/modules/image/src/Entity/ImageStyle.php
index a87554c..59eb2b6 100644
--- a/core/modules/image/src/Entity/ImageStyle.php
+++ b/core/modules/image/src/Entity/ImageStyle.php
@@ -14,6 +14,7 @@
 use Drupal\Core\Entity\EntityWithPluginCollectionInterface;
 use Drupal\Core\Routing\RequestHelper;
 use Drupal\Core\Site\Settings;
+use Drupal\Core\Url;
 use Drupal\image\ImageEffectPluginCollection;
 use Drupal\image\ImageEffectInterface;
 use Drupal\image\ImageStyleInterface;
@@ -222,7 +223,7 @@ public function buildUrl($path, $clean_urls = NULL) {
     // actual file path, this avoids bootstrapping PHP once the files are built.
     if ($clean_urls === FALSE && file_uri_scheme($uri) == 'public' && !file_exists($uri)) {
       $directory_path = file_stream_wrapper_get_instance_by_uri($uri)->getDirectoryPath();
-      return _url($directory_path . '/' . file_uri_target($uri), array('absolute' => TRUE, 'query' => $token_query));
+      return Url::fromUri('base://' . $directory_path . '/' . file_uri_target($uri), array('absolute' => TRUE, 'query' => $token_query))->toString();
     }
 
     $file_url = file_create_url($uri);
diff --git a/core/tests/Drupal/Tests/Core/Utility/UnroutedUrlAssemblerTest.php b/core/tests/Drupal/Tests/Core/Utility/UnroutedUrlAssemblerTest.php
index 4c6272a..7bd4836 100644
--- a/core/tests/Drupal/Tests/Core/Utility/UnroutedUrlAssemblerTest.php
+++ b/core/tests/Drupal/Tests/Core/Utility/UnroutedUrlAssemblerTest.php
@@ -73,6 +73,7 @@ public function testAssembleWithNeitherExternalNorDomainLocalUri() {
    * @dataProvider providerTestAssembleWithExternalUrl
    */
   public function testAssembleWithExternalUrl($uri, array $options, $expected) {
+   $this->setupRequestStack(FALSE);
    $this->assertEquals($expected, $this->unroutedUrlAssembler->assemble($uri, $options));
   }