diff -u b/core/modules/system/lib/Drupal/system/Tests/System/ShutdownFunctionsTest.php b/core/modules/system/lib/Drupal/system/Tests/System/ShutdownFunctionsTest.php
--- b/core/modules/system/lib/Drupal/system/Tests/System/ShutdownFunctionsTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/System/ShutdownFunctionsTest.php
@@ -39,11 +39,13 @@
     $this->assertEqual(\Drupal::state()->get('_system_test_first_shutdown_function'), array($arg1, $arg2));
     $this->assertEqual(\Drupal::state()->get('_system_test_second_shutdown_function'), array($arg1, $arg2));
 
-    if (!function_exists('fastcgi_finish_request')) {
-      // If using PHP-FPM then fastcgi_finish_request() will have been fired
-      // preventing further output to the browser. Make sure exceptions
-      // displayed through \Drupal\Core\Utility\Error::renderExceptionSafe() are
-      // correctly escaped.
+    // If using PHP-FPM then fastcgi_finish_request() will have been fired
+    // preventing further output to the browser.
+    // @see \Drupal\system_test\Controller\SystemTestController::shutdownFunctions()
+    if (strpos($this->drupalGetContent(), 'The function fastcgi_finish_request exists when serving the request.') === FALSE) {
+      // Make sure exceptions displayed through
+      // \Drupal\Core\Utility\Error::renderExceptionSafe() are correctly
+      // escaped.
       $this->assertRaw('Drupal is <blink>awesome</blink>.');
     }
   }
only in patch2:
unchanged:
--- a/core/modules/system/tests/modules/system_test/lib/Drupal/system_test/Controller/SystemTestController.php
+++ b/core/modules/system/tests/modules/system_test/lib/Drupal/system_test/Controller/SystemTestController.php
@@ -68,6 +68,14 @@ public function setHeader() {
    */
   public function shutdownFunctions($arg1, $arg2) {
     system_test_page_shutdown_functions($arg1, $arg2);
+    // If using PHP-FPM then fastcgi_finish_request() will have been fired
+    // preventing further output to the browser which means that the escaping of
+    // the exception message can not be tested.
+    // @see _drupal_shutdown_function()
+    // @see \Drupal\system\Tests\System\ShutdownFunctionsTest
+    if (function_exists('fastcgi_finish_request')) {
+      return 'The function fastcgi_finish_request exists when serving the request.';
+    }
   }
 
 }