diff --git a/core/lib/Drupal/Component/Utility/Xss.php b/core/lib/Drupal/Component/Utility/Xss.php
index adbea58..60c3c08 100644
--- a/core/lib/Drupal/Component/Utility/Xss.php
+++ b/core/lib/Drupal/Component/Utility/Xss.php
@@ -39,7 +39,7 @@ class Xss {
    *
    * @see \Drupal\Component\Utility\Xss::filter()
    */
-  protected static $safeAttributes = ['alt', 'title'];
+  protected static $safeAttributes = array('alt', 'title');
 
   /**
    * The default list of RDFa attributes untouched by filter().
@@ -49,7 +49,7 @@ class Xss {
    * @see \Drupal\Component\Utility\Xss::filter()
    * @see http://www.w3.org/TR/xhtml-rdfa/
    */
-  protected static $rdfaAttributes = ['property', 'typeof', 'rel', 'rev', 'datatype'];
+  protected static $rdfaAttributes = array('property', 'typeof', 'rel', 'rev', 'datatype');
 
   /**
    * Filters HTML to prevent cross-site-scripting (XSS) vulnerabilities.
@@ -346,7 +346,7 @@ protected static function filterProtocol($name, $value) {
     // If the value matches the typical namespace:value pattern used in RDFa,
     // return it directly. Otherwise, filter it.
     if (in_array($name, static::$rdfaAttributes)) {
-      return preg_match('/^[[:alnum:]]+\:[[:alnum:]]+$/', $value) ? $value : UrlHelper::stripDangerousProtocols($value);
+      return preg_match('/[a-zA-Z0-9]+\:[a-zA-Z0-9]+$/', $value) ? $value : UrlHelper::stripDangerousProtocols($value);
     }
     else {
       return UrlHelper::filterBadProtocol($value);