diff --git a/core/modules/system/src/Plugin/Block/SystemMenuBlock.php b/core/modules/system/src/Plugin/Block/SystemMenuBlock.php
index 4a6a2ea..843ca15 100644
--- a/core/modules/system/src/Plugin/Block/SystemMenuBlock.php
+++ b/core/modules/system/src/Plugin/Block/SystemMenuBlock.php
@@ -191,8 +191,17 @@ public function getCacheContexts() {
     $menu_name = $this->getDerivativeId();
     return [
       'user.roles',
+      // @todo Bubble up contexts from menu.
       'route.menu_active_trails:' . $menu_name,
     ];
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function isCacheable() {
+    // Menu blocks leverage menu tree cache.
+    return FALSE;
+  }
+
 }