diff -u b/core/modules/taxonomy/src/Plugin/views/filter/TaxonomyIndexTid.php b/core/modules/taxonomy/src/Plugin/views/filter/TaxonomyIndexTid.php
--- b/core/modules/taxonomy/src/Plugin/views/filter/TaxonomyIndexTid.php
+++ b/core/modules/taxonomy/src/Plugin/views/filter/TaxonomyIndexTid.php
@@ -2,6 +2,7 @@
 
 namespace Drupal\taxonomy\Plugin\views\filter;
 
+use Drupal\Core\Cache\Cache;
 use Drupal\Core\Entity\Element\EntityAutocomplete;
 use Drupal\Core\Form\FormStateInterface;
 use Drupal\taxonomy\Entity\Term;
@@ -386,15 +387,15 @@
    * {@inheritdoc}
    */
   public function getCacheTags() {
-    $cache_tags = parent::getCacheTags();
+    $tags = parent::getCacheTags();
     $vocabulary = $this->vocabularyStorage->load($this->options['vid']);
     if ($vocabulary) {
-      $cache_tags += $vocabulary->getCacheTags();
+      $tags = Cache::mergeTags($tags, $vocabulary->getCacheTags());
     }
     // There is no vocabulary specific tag for 'taxonomy_term_list' so we add
-    // the generic tag here to catch any updates to tags.
-    $cache_tags[] = 'taxonomy_term_list';
-    return $cache_tags;
+    // the generic tag here to catch any updates to terms.
+    $tags = Cache::mergeTags($tags, ['taxonomy_term_list']);
+    return $tags;
   }
 
   /**