diff --git a/includes/unicode.inc b/includes/unicode.inc
index fd497cc..7340ecd 100644
--- a/includes/unicode.inc
+++ b/includes/unicode.inc
@@ -341,7 +341,7 @@ function truncate_utf8($string, $max_length, $wordsafe = FALSE, $add_ellipsis =
     // 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 . '})[' . PREG_CLASS_UNICODE_WORD_BOUNDARY . ']/u', $string, $matches);
+    $found = preg_match('/^(.{' . $min_wordsafe_length . ',' . $max_length . '})[' . PREG_CLASS_UNICODE_WORD_BOUNDARY . ']/us', $string, $matches);
     if ($found) {
       $string = $matches[1];
     }