diff --git a/include/class-MailboxSizeAPI.php b/include/class-MailboxSizeAPI.php
index 60a4ab7..4b9e9ab 100644
--- a/include/class-MailboxSizeAPI.php
+++ b/include/class-MailboxSizeAPI.php
@@ -1,89 +1,89 @@
 <?php
 # Copyright (C) 2018, 2019, 2020 Valerio Bozzolan
 # KISS Libre Hosting Panel
 #
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU Affero General Public License as
 # published by the Free Software Foundation, either version 3 of the
 # License, or (at your option) any later version.
 #
 # This program is distributed in the hope that it will be useful,
 # but WITHOUT ANY WARRANTY; without even the implied warranty of
 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 # GNU Affero General Public License for more details.
 #
 # You should have received a copy of the GNU General Public License
 # along with this program. If not, see <http://www.gnu.org/licenses/>.
 
 // load dependend traits
 class_exists( 'MailboxAPI' );
 
 /**
  * Methods for a MailboxSizeAPI class
  */
 trait MailboxSizeAPITrait {
 
 	use MailboxAPITrait;
 
 	/**
 	 * Select the MAX Mailbox quota date
 	 *
 	 * @return self
 	 */
 	public function selectMaxMailboxSizeDate() {
 		return $this->select( 'MAX( mailboxsize_date ) AS max_mailboxsize_date' )
-		            ->groupBy(     'mailboxsize_date' );
+		            ->groupBy( 'mailbox_ID' );
 	}
 
 	/**
 	 * Assure that this is only the more updated Mailbox quota
 	 *
 	 * @return self
 	 */
 	public function whereMailboxSizeIsLast() {
 
 		// subquery with a maximum constraint
 		$max = ( new MailboxSizeAPI( null, false ) )
 			->fromCustom( DB::instance()->getTable( 'mailboxsize', 'mailboxsize_sub' ) )
 			->equals( 'mailboxsize.mailbox_ID', 'mailboxsize_sub.mailbox_ID' )
 			->selectMaxMailboxSizeDate()
 			->getQuery();
 
 		return $this->where( sprintf( 'mailboxsize_date = (%s)', $max ) );
 	}
 }
 
 /**
  * MailboxSize API
  */
 class MailboxSizeAPI extends Query {
 
 	use MailboxSizeAPITrait;
 
 	/**
 	 * Univoque column name to the Mailbox ID
 	 */
 	protected $MAILBOX_ID = 'mailboxsize.mailbox_ID';
 
 	/**
 	 * Constructor
 	 *
 	 * @param object $db   Database
 	 * @param mixed  $from Set to false to avoid to use the default FROM
 	 */
 	public function __construct( $db = null, $from = true ) {
 
 		// set database and class name
 		parent::__construct( $db, MailboxSize::class );
 
 		/**
 		 * Set database table (sometime the standard alias it's not useful)
 		 *
 		 * See MailboxSizeAPI class.
 		 */
 		if( $from ) {
 			$this->from( MailboxSize::T );
 		}
 	}
 
 }