core/lib/Drupal/Core/EventSubscriber/SmartCacheSubscriber.php      | 7 +++++++
 core/lib/Drupal/Core/Render/MainContent/SmartCacheHtmlRenderer.php | 7 +++++++
 2 files changed, 14 insertions(+)

diff --git a/core/lib/Drupal/Core/EventSubscriber/SmartCacheSubscriber.php b/core/lib/Drupal/Core/EventSubscriber/SmartCacheSubscriber.php
index 93dc74e..00d5972 100644
--- a/core/lib/Drupal/Core/EventSubscriber/SmartCacheSubscriber.php
+++ b/core/lib/Drupal/Core/EventSubscriber/SmartCacheSubscriber.php
@@ -80,6 +80,13 @@ public function onRouteMatch(GetResponseEvent $event) {
       return;
     }
 
+    // @todo For now, SmartCache doesn't handle admin routes. It may be too much
+    //   work to add the necessary cacheability metadata to all admin routes
+    //   before 8.0.0, but that can happen in 8.1.0 without a BC break.
+    if ($this->routeMatch->getRouteObject()->getOption('_admin_route')) {
+      return;
+    }
+
     $this->routeMatch->getRouteName();
 
     // Get the contexts by which the current route's response must be varied.
diff --git a/core/lib/Drupal/Core/Render/MainContent/SmartCacheHtmlRenderer.php b/core/lib/Drupal/Core/Render/MainContent/SmartCacheHtmlRenderer.php
index 133499d..26dc5ba 100644
--- a/core/lib/Drupal/Core/Render/MainContent/SmartCacheHtmlRenderer.php
+++ b/core/lib/Drupal/Core/Render/MainContent/SmartCacheHtmlRenderer.php
@@ -95,6 +95,13 @@ protected function finish(array $html) {
       return parent::finish($html);
     }
 
+    // @todo For now, SmartCache doesn't handle admin routes. It may be too much
+    //   work to add the necessary cacheability metadata to all admin routes
+    //   before 8.0.0, but that can happen in 8.1.0 without a BC break.
+    if ($this->routeMatch->getRouteObject()->getOption('_admin_route')) {
+      return parent::finish($html);
+    }
+
     $cacheable_html = $html;
 
     // Get the contexts by which the current route's response must be varied.