diff --git a/sql/mysql-compatibility.md b/sql/mysql-compatibility.md
index 189de50550ac..3e1de7690960 100644
--- a/sql/mysql-compatibility.md
+++ b/sql/mysql-compatibility.md
@@ -28,6 +28,7 @@ TiDB 支持包括跨行事务、JOIN 及子查询在内的绝大多数 MySQL 5.7
 * 删除主键
 * SYS schema
 * MySQL 追踪优化器
+* X Protocol
 
 ## 与 MySQL 有差异的特性