diff --git a/core/lib/Drupal/Core/Render/MainContent/HtmlRenderer.php b/core/lib/Drupal/Core/Render/MainContent/HtmlRenderer.php
index 48adfc1..55a495c 100644
--- a/core/lib/Drupal/Core/Render/MainContent/HtmlRenderer.php
+++ b/core/lib/Drupal/Core/Render/MainContent/HtmlRenderer.php
@@ -186,6 +186,10 @@ public function renderResponse(array $main_content, Request $request, RouteMatch
         if (count($page_parts) !== 2) {
           throw new \LogicException("You need to have only one body or one <!-- X-RENDER-CACHE-BIG-PIPE-SPLIT --> tag in your html.html.twig template file.");
         }
+
+        // Support streaming on NGINX + php-fpm (nginx >= 1.5.6).
+        header('X-Accel-Buffering: no');
+
         print $page_parts[0];
 
         // @todo Add helper function.
@@ -197,9 +201,6 @@ public function renderResponse(array $main_content, Request $request, RouteMatch
 EOF;
         print $behaviors;
 
-        // Support streaming on NGINX + php-fpm (nginx >= 1.5.6).
-        header('X-Accel-Buffering: no');
-
         ob_end_flush();
         flush();
 
diff --git a/core/lib/Drupal/Core/Render/RenderCache.php b/core/lib/Drupal/Core/Render/RenderCache.php
index 20a4298..48bb480 100644
--- a/core/lib/Drupal/Core/Render/RenderCache.php
+++ b/core/lib/Drupal/Core/Render/RenderCache.php
@@ -182,7 +182,7 @@ protected function checkPlaceholders(array $placeholders) {
    *   The render array placeholder.
    */
   protected function createRenderCacheArrayPlaceholder(array $elements, $data = FALSE) {
-    $render_cache_array = array_intersect_key($elements, ['#cache' => 0, '#pre_render_cache' => 1]);
+    $render_cache_array = array_intersect_key($elements, ['#cache' => 0, '#pre_render_cache' => 1, '#render_strategies' => 2]);
 
     $placeholder_keys = [];
     if (isset($render_cache_array['#cache']['keys'])) {
@@ -191,6 +191,11 @@ protected function createRenderCacheArrayPlaceholder(array $elements, $data = FA
     if (isset($render_cache_array['#pre_render_cache'])) {
       $placeholder_keys = array_merge($placeholder_keys, array_keys($render_cache_array['#pre_render_cache']));
     }
+    // Make it simpler for strategies to check supported strategies.
+    if (!empty($render_cache_array['#render_strategies'])) {
+      $render_cache_array['#render_strategies'] = array_combine($render_cache_array['#render_strategies'], $render_cache_array['#render_strategies']);
+    }
+
     $placeholder_keys[] = hash('sha1', serialize($render_cache_array));
 
     // @todo Use hash of $pre_bubbling_elements['#pre_render_cache','#cache']?
diff --git a/core/lib/Drupal/Core/Render/Renderer.php b/core/lib/Drupal/Core/Render/Renderer.php
index 7bd26e5..f605ae0 100644
--- a/core/lib/Drupal/Core/Render/Renderer.php
+++ b/core/lib/Drupal/Core/Render/Renderer.php
@@ -555,7 +555,7 @@ protected function processPlaceholders(array &$elements) {
       // @todo Render strategies will need to take care of this.
       global $process_remaining_placeholders;
 
-      if (isset($process_remaining_placeholders)) {
+      if (isset($process_remaining_placeholders) || (isset($placeholder_elements['#render_strategies']['single_flush']))) {
         $markup = $this->renderPlaceholder($placeholder, $placeholder_elements);
         $elements['#markup'] = str_replace('<div id="' . $placeholder . '"></div>', $markup, $elements['#markup']);
         unset($elements['#cache']['placeholders'][$placeholder]);