diff --git a/phpBB/phpbb/db/driver/mssql_base.php b/phpBB/phpbb/db/driver/mssql_base.php
index 514df9eaca..98d16ca7fc 100644
--- a/phpBB/phpbb/db/driver/mssql_base.php
+++ b/phpBB/phpbb/db/driver/mssql_base.php
@@ -60,6 +60,14 @@ abstract class mssql_base extends \phpbb\db\driver\driver
 		return $expression . " ESCAPE '\\'";
 	}
 
+	/**
+	* {@inheritDoc}
+	*/
+	function cast_expr_to_bigint($expression)
+	{
+		return 'CONVERT(BIGINT, ' . $expression . ')';
+	}
+
 	/**
 	* Build db-specific query data
 	* @access private