diff --git a/core/tests/Drupal/Tests/Component/Utility/HtmlTest.php b/core/tests/Drupal/Tests/Component/Utility/HtmlTest.php
index 3638408a02..1860e04105 100644
--- a/core/tests/Drupal/Tests/Component/Utility/HtmlTest.php
+++ b/core/tests/Drupal/Tests/Component/Utility/HtmlTest.php
@@ -67,9 +67,10 @@ public function providerTestCleanCssIdentifier() {
       [$id1, $id1, []],
       // Verify that valid UTF-8 characters are not stripped from the identifier.
       [$id2, $id2, []],
-      // Verify that invalid characters (including non-breaking space) are stripped from the identifier.
-      [$id3, $id3],
       // Verify that double underscores are not stripped from the identifier.
+      [$id3, $id3],
+      // Verify that invalid characters (including non-breaking space) are
+      // stripped from the identifier.
       ['invalididentifier', 'invalid !"#$%&\'()*+,./:;<=>?@[\\]^`{|}~ identifier', []],
       // Verify that an identifier starting with a digit is replaced.
       ['_cssidentifier', '1cssidentifier', []],