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([