diff --git a/core/lib/Drupal/Component/Utility/Unicode.php b/core/lib/Drupal/Component/Utility/Unicode.php
index c5e0d82..1f63f88 100644
--- a/core/lib/Drupal/Component/Utility/Unicode.php
+++ b/core/lib/Drupal/Component/Utility/Unicode.php
@@ -479,7 +479,7 @@ public static function truncate($string, $max_length, $wordsafe = FALSE, $add_el
       // Find the last word boundary, if there is one within $min_wordsafe_length
       // to $max_length characters. preg_match() is always greedy, so it will
       // find the longest string possible.
-      $found = preg_match('/^(.{' . $min_wordsafe_length . ',' . $max_length . '})[' . Unicode::PREG_CLASS_WORD_BOUNDARY . ']/u', $string, $matches);
+      $found = preg_match('/^(.{' . $min_wordsafe_length . ',' . $max_length . '})[' . Unicode::PREG_CLASS_WORD_BOUNDARY . ']/us', $string, $matches);
       if ($found) {
         $string = $matches[1];
       }