diff --git a/src/SearchWordHighlighter.php b/src/SearchWordHighlighter.php
index 72f4fb5..d81cb16 100644
--- a/src/SearchWordHighlighter.php
+++ b/src/SearchWordHighlighter.php
@@ -92,7 +92,7 @@ public function highlight($words)
         });
 
         // replace chained whitespace with a single space
-        $string = preg_replace('/[\s]+/s', ' ', $this->string);
+        $string = preg_replace('/[\s]+/us', ' ', $this->string);
         $string = html_entity_decode($string);
 
         if ($this->wordsBeforeMatch > 0) {