diff --git a/src/Plugin/Block/AlertBannerBlock.php b/src/Plugin/Block/AlertBannerBlock.php
index 5e62de6..e04cacc 100644
--- a/src/Plugin/Block/AlertBannerBlock.php
+++ b/src/Plugin/Block/AlertBannerBlock.php
@@ -146,9 +146,7 @@ public function build() {
 
     // Render the alert banner.
     $build = [];
-    $contexts = [];
     foreach ($published_alert_banners as $alert_banner) {
-      $contexts = Cache::mergeContexts($contexts, $alert_banner->getCacheContexts());
 
       // Only add to the build if it is visible.
       // @see #154.
@@ -157,7 +155,6 @@ public function build() {
           ->view($alert_banner);
       }
     }
-    $build['#cache']['contexts'] = $contexts;
     return $build;
   }
 
@@ -227,6 +224,17 @@ protected function mapTypesConfigToQuery() : array {
     });
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function getCacheContexts() {
+    $contexts = [];
+    foreach ($this->getCurrentAlertBanners() as $alert_banner) {
+      $contexts = Cache::mergeContexts($contexts, $alert_banner->getCacheContexts());
+    }
+    return Cache::mergeContexts(parent::getCacheContexts(), $contexts);
+  }
+
   /**
    * {@inheritdoc}
    */