diff --git a/src/php/tests/interop/interop_client.php b/src/php/tests/interop/interop_client.php
index 6670ef3ab9c29cf3a0db06ed5fd1e55b356fc735..5965097e1877aef1ed10a585d16aa85fee55691d 100755
--- a/src/php/tests/interop/interop_client.php
+++ b/src/php/tests/interop/interop_client.php
@@ -33,7 +33,6 @@
  */
 require_once realpath(dirname(__FILE__) . '/../../vendor/autoload.php');
 require 'empty.php';
-require 'message_set.php';
 require 'messages.php';
 require 'test.php';
 use Google\Auth\CredentialsLoader;