diff --git a/src/Behat/Mink/WebAssert.php b/src/Behat/Mink/WebAssert.php
index 147f8f9dd..c92def38a 100644
--- a/src/Behat/Mink/WebAssert.php
+++ b/src/Behat/Mink/WebAssert.php
@@ -168,7 +168,7 @@ public function statusCodeNotEquals($code)
     public function pageTextContains($text)
     {
         $actual = $this->session->getPage()->getText();
-        $actual = preg_replace('/\s+/', ' ', $actual);
+        $actual = preg_replace('/\s+/u', ' ', $actual);
         $regex  = '/'.preg_quote($text, '/').'/ui';
 
         if (!preg_match($regex, $actual)) {
@@ -187,7 +187,7 @@ public function pageTextContains($text)
     public function pageTextNotContains($text)
     {
         $actual = $this->session->getPage()->getText();
-        $actual = preg_replace('/\s+/', ' ', $actual);
+        $actual = preg_replace('/\s+/u', ' ', $actual);
         $regex  = '/'.preg_quote($text, '/').'/ui';
 
         if (preg_match($regex, $actual)) {