diff --git a/public/main/inc/lib/api.lib.php b/public/main/inc/lib/api.lib.php
index d504d6e5bb..f21bbf486b 100644
--- a/public/main/inc/lib/api.lib.php
+++ b/public/main/inc/lib/api.lib.php
@@ -294,7 +294,7 @@ define('LOG_SURVEY_ID', 'survey_id');
 define('LOG_SURVEY_CREATED', 'survey_created');
 define('LOG_SURVEY_DELETED', 'survey_deleted');
 define('LOG_SURVEY_CLEAN_RESULTS', 'survey_clean_results');
-define('USERNAME_PURIFIER', '/[^0-9A-Za-z_\.\$-]/');
+define('USERNAME_PURIFIER', '/[^0-9A-Za-z_\.@\$-]/');
 
 //used when login_is_email setting is true
 define('USERNAME_PURIFIER_MAIL', '/[^0-9A-Za-z_\.@]/');
diff --git a/public/main/inc/lib/usermanager.lib.php b/public/main/inc/lib/usermanager.lib.php
index 7cf7ae812f..07ccc8e396 100644
--- a/public/main/inc/lib/usermanager.lib.php
+++ b/public/main/inc/lib/usermanager.lib.php
@@ -1387,6 +1387,9 @@ class UserManager
             $return = 'true' === api_get_setting('login_is_email') ? substr(preg_replace(USERNAME_PURIFIER_MAIL, '', $username), 0, User::USERNAME_MAX_LENGTH) : substr(preg_replace(USERNAME_PURIFIER, '', $username), 0, User::USERNAME_MAX_LENGTH);
             $return = URLify::transliterate($return);
 
+            // We want everything transliterate() does except converting @ to '(at)'. This is a hack to avoid this.
+            $return = str_replace(' (at) ', '@', $return);
+
             return $return;
         }