diff --git a/core/lib/Drupal/Component/Utility/Xss.php b/core/lib/Drupal/Component/Utility/Xss.php
index 4c6e812..5d5ba97 100644
--- a/core/lib/Drupal/Component/Utility/Xss.php
+++ b/core/lib/Drupal/Component/Utility/Xss.php
@@ -175,7 +175,7 @@ protected static function split($string, $html_tags, $class) {
     $xhtml_slash = $count ? ' /' : '';
 
     // Clean up attributes.
-    $attr2 = implode(' ', $class::attributes($attrlist));
+    $attr2 = implode(' ', $class::attributes(trim($attrlist)));
     $attr2 = preg_replace('/[<>]/', '', $attr2);
     $attr2 = strlen($attr2) ? ' ' . $attr2 : '';