diff --git a/core/modules/simpletest/tests/fixtures/simpletest_phpunit_run_command_test.php b/core/modules/simpletest/tests/fixtures/simpletest_phpunit_run_command_test.php
index 839f008..2a01d30 100644
--- a/core/modules/simpletest/tests/fixtures/simpletest_phpunit_run_command_test.php
+++ b/core/modules/simpletest/tests/fixtures/simpletest_phpunit_run_command_test.php
@@ -10,6 +10,9 @@
  * To avoid accidentally running, it is not in a normal PSR-4 directory, the
  * file name does not adhere to PSR-4 and an environment variable also needs to
  * be set for the crash to happen.
+ *
+ * @runTestsInSeparateProcesses
+ * @preserveGlobalState disabled
  */
 class SimpletestPhpunitRunCommandTestWillDie extends UnitTestCase {