diff --git a/core/includes/bootstrap.inc b/core/includes/bootstrap.inc
index b358269..1e58e38 100644
--- a/core/includes/bootstrap.inc
+++ b/core/includes/bootstrap.inc
@@ -2396,10 +2396,6 @@ function _drupal_bootstrap_variables() {
  */
 function _drupal_bootstrap_page_header() {
   bootstrap_invoke_all('boot');
-
-  if (!drupal_is_cli()) {
-    ob_start();
-  }
 }
 
 /**
diff --git a/core/lib/Drupal/Core/EventSubscriber/RequestCloseSubscriber.php b/core/lib/Drupal/Core/EventSubscriber/RequestCloseSubscriber.php
index 6305164..5445749 100644
--- a/core/lib/Drupal/Core/EventSubscriber/RequestCloseSubscriber.php
+++ b/core/lib/Drupal/Core/EventSubscriber/RequestCloseSubscriber.php
@@ -40,9 +40,6 @@ class RequestCloseSubscriber implements EventSubscriberInterface {
     if ($config->get('cache') && ($cache = drupal_page_set_cache())) {
       drupal_serve_page_from_cache($cache);
     }
-    else {
-      ob_flush();
-    }
 
     _registry_check_code(REGISTRY_WRITE_LOOKUP_CACHE);
     drupal_cache_system_paths();