diff --git a/src/Utility/InjectCssFileUtility.php b/src/Utility/InjectCssFileUtility.php
index 5d94114..01efd88 100644
--- a/src/Utility/InjectCssFileUtility.php
+++ b/src/Utility/InjectCssFileUtility.php
@@ -21,9 +21,9 @@ class InjectCssFileUtility {
    */
   public static function getRelativePath(bool $admin = FALSE): string {
     if ($admin) {
-      return file_url_transform_relative(file_create_url(static::FILE_PATH_ADMIN));
+      return \Drupal::service('file_url_generator')->generateString(static::FILE_PATH_ADMIN);
     }
-    return file_url_transform_relative(file_create_url(static::FILE_PATH));
+    return \Drupal::service('file_url_generator')->generateString(static::FILE_PATH);
   }
 
 }
diff --git a/tests/src/FunctionalJavascript/SimpleLiveCssTest.php b/tests/src/FunctionalJavascript/SimpleLiveCssTest.php
index 586c9af..c6e0d29 100644
--- a/tests/src/FunctionalJavascript/SimpleLiveCssTest.php
+++ b/tests/src/FunctionalJavascript/SimpleLiveCssTest.php
@@ -35,7 +35,7 @@ class SimpleLiveCssTest extends WebDriverTestBase {
   /**
    * {@inheritdoc}
    */
-  protected function setUp() {
+  protected function setUp(): void {
     parent::setUp();
 
     $this->user = $this->drupalCreateUser([