diff --git a/tests/php/View/Embed/MockResponse.php b/tests/php/View/Embed/MockResponse.php
index 65785047afd..872436cf4e4 100644
--- a/tests/php/View/Embed/MockResponse.php
+++ b/tests/php/View/Embed/MockResponse.php
@@ -56,6 +56,9 @@ public function getHeader($name)
 
     public function getHeaderLine($name)
     {
+        if (strtolower($name) === 'content-type') {
+            return 'text/html; charset=utf-8';
+        }
         return '';
     }