diff --git a/core/modules/views/lib/Drupal/views/Plugin/views/cache/CachePluginBase.php b/core/modules/views/lib/Drupal/views/Plugin/views/cache/CachePluginBase.php
index 3f51143..486543f 100644
--- a/core/modules/views/lib/Drupal/views/Plugin/views/cache/CachePluginBase.php
+++ b/core/modules/views/lib/Drupal/views/Plugin/views/cache/CachePluginBase.php
@@ -94,7 +94,8 @@ public function summaryTitle() {
    * @param $type
    *   The cache type, either 'query', 'result' or 'output'.
    */
-  protected function cacheExpire($type) { }
+  protected function cacheExpire($type) {
+  }
 
    /**
     * Determine expiration time in the cache table of the cache type
@@ -333,16 +334,17 @@ public function generateOutputKey() {
    */
   protected function getCacheTags() {
     $tags = array();
+
     $entity_information = $this->view->query->getEntityInformation();
 
     if (!empty($entity_information)) {
       $tags[$this->view->storage->id()] = TRUE;
-      // Add an ENTIY_TYPE_view tag for each entity type used by this view.
+      // Add an ENTITY_TYPE_view tag for each entity type used by this view.
       foreach (array_keys($entity_information) as $type) {
         $tags[$type . '_view'] = TRUE;
       }
 
-      // Collect entity IDs too if there are view results.
+      // Collect entity IDs if there are view results.
       if (!empty($this->view->result)) {
         foreach ($this->view->result as $result) {
           $type = $result->_entity->entityType();
@@ -360,7 +362,10 @@ protected function getCacheTags() {
       }
     }
 
-    return $tags;
+    // Filter out any duplicate values from generated tags.
+    return array_map(function($item) {
+      return is_array($item) ? array_unique($item) : $item;
+    }, $tags);
   }
 
 }