diff --git a/tests/external/external_get_users_test.php b/tests/external/external_get_users_test.php
index 558c2d1..ec3ddc6 100644
--- a/tests/external/external_get_users_test.php
+++ b/tests/external/external_get_users_test.php
@@ -31,6 +31,7 @@
  * @category  external
  * @copyright 2020 The Open University
  * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ * @runTestsInSeparateProcesses
  */
 class external_get_users_test extends \externallib_advanced_testcase {