diff --git a/core/modules/search/src/Plugin/SearchInterface.php b/core/modules/search/src/Plugin/SearchInterface.php
index ab247b3..2eea586 100644
--- a/core/modules/search/src/Plugin/SearchInterface.php
+++ b/core/modules/search/src/Plugin/SearchInterface.php
@@ -94,8 +94,8 @@ public function execute();
    *     or an empty array if there are no results.
    *   - cache_tags: An array that holds all the cache tags associated
    *     with the items.
-   *   - cache_contexts: (optional) An array which holds the contexts for the
-   *     search page and all items in the items array.
+   *   - cache_contexts: An array which holds the contexts for the search page
+   *     and all items in the items array.
    */
   public function buildResults();
 
diff --git a/core/modules/search/src/Plugin/SearchPluginBase.php b/core/modules/search/src/Plugin/SearchPluginBase.php
index 425be87..8ebb8a4 100644
--- a/core/modules/search/src/Plugin/SearchPluginBase.php
+++ b/core/modules/search/src/Plugin/SearchPluginBase.php
@@ -111,12 +111,10 @@ public function buildResults() {
         '#plugin_id' => $this->getPluginId(),
       );
       $built['cache_tags'] = Cache::mergeTags($built['cache_tags'], $result['cache_tags']);
-      if (isset($result['cache_contexts'])) {
-        $built['cache_contexts'] = Cache::mergeContexts(
-          $built['cache_contexts'],
-          $result['cache_contexts']
-        );
-      }
+      $built['cache_contexts'] = Cache::mergeContexts(
+        $built['cache_contexts'],
+        $result['cache_contexts']
+      );
     }
 
     return $built;
diff --git a/core/modules/user/src/Plugin/Search/UserSearch.php b/core/modules/user/src/Plugin/Search/UserSearch.php
index 0d2b46e..a842c1d 100644
--- a/core/modules/user/src/Plugin/Search/UserSearch.php
+++ b/core/modules/user/src/Plugin/Search/UserSearch.php
@@ -155,6 +155,8 @@ public function execute() {
         $result['title'] .= ' (' . $account->getEmail() . ')';
       }
       $result['cache_tags'] = $account->getCacheTags();
+      $result['cache_tags'][] = 'user:list';
+      $result['cache_contexts'] = array();
       $results[] = $result;
     }