diff --git a/lib/messagelib.php b/lib/messagelib.php
index deca4e615d7..3fcaa94c6ea 100644
--- a/lib/messagelib.php
+++ b/lib/messagelib.php
@@ -295,8 +295,7 @@ function message_send(\core\message\message $eventdata) {
         if (!empty($eventdata->convid)) {
             // Cache the timecreated value of the last message in this conversation.
             $cache = cache::make('core', 'message_time_last_message_in_conversation');
-            $key = \core_message\helper::get_last_message_time_created_cache_key($eventdata->convid);
-            $cache->set($key, $tabledata->timecreated);
+            $cache->set($eventdata->convid, $tabledata->timecreated);
         }
     }
 
diff --git a/message/classes/api.php b/message/classes/api.php
index 58fec61dab9..4eccf2be9b0 100644
--- a/message/classes/api.php
+++ b/message/classes/api.php
@@ -617,9 +617,8 @@ class api {
             }
 
             // Check the cache to see if we even need to do a DB query.
-            $cache = \cache::make('core', 'message_time_last_message_between_users');
-            $key = helper::get_last_message_time_created_cache_key($conversationid);
-            $lastcreated = $cache->get($key);
+            $cache = \cache::make('core', 'message_time_last_message_in_conversation');
+            $lastcreated = $cache->get($conversationid);
 
             // The last known message time is earlier than the one being requested so we can
             // just return an empty result set rather than having to query the DB.
@@ -655,8 +654,7 @@ class api {
         if (!empty($timefrom)) {
             // Check the cache to see if we even need to do a DB query.
             $cache = \cache::make('core', 'message_time_last_message_in_conversation');
-            $key = helper::get_last_message_time_created_cache_key($convid);
-            $lastcreated = $cache->get($key);
+            $lastcreated = $cache->get($convid);
 
             // The last known message time is earlier than the one being requested so we can
             // just return an empty result set rather than having to query the DB.
diff --git a/message/classes/helper.php b/message/classes/helper.php
index 0e35f67ab8f..237cd7c36aa 100644
--- a/message/classes/helper.php
+++ b/message/classes/helper.php
@@ -439,16 +439,6 @@ class helper {
         return sha1(implode('-', $userids));
     }
 
-    /**
-     * Returns the cache key for the time created value of the last message of this conversation.
-     *
-     * @param int $convid The conversation identifier.
-     * @return string The key.
-     */
-    public static function get_last_message_time_created_cache_key(int $convid) {
-        return $convid;
-    }
-
     /**
      * Checks if legacy messages exist for a given user.
      *