diff --git a/core/lib/Drupal/Core/EventSubscriber/FinishResponseSubscriber.php b/core/lib/Drupal/Core/EventSubscriber/FinishResponseSubscriber.php
index 251b920..86d2aa7 100644
--- a/core/lib/Drupal/Core/EventSubscriber/FinishResponseSubscriber.php
+++ b/core/lib/Drupal/Core/EventSubscriber/FinishResponseSubscriber.php
@@ -124,10 +124,11 @@ public function onRespond(FilterResponseEvent $event) {
     }
 
     $is_cacheable = ($this->requestPolicy->check($request) === RequestPolicyInterface::ALLOW) && ($this->responsePolicy->check($response, $request) !== ResponsePolicyInterface::DENY);
+    $is_cacheable_response = ($response instanceof CacheableResponseInterface);
 
     // Add headers necessary to specify whether the response should be cached by
     // proxies and/or the browser.
-    if ($is_cacheable && $this->config->get('cache.page.max_age') > 0) {
+    if ($is_cacheable && $is_cacheable_response && $this->config->get('cache.page.max_age') > 0) {
       if (!$this->isCacheControlCustomized($response)) {
         // Only add the default Cache-Control header if the controller did not
         // specify one on the response.