diff --git a/tidbcloudy/specification.py b/tidbcloudy/specification.py
index c2f49f6..d92b300 100644
--- a/tidbcloudy/specification.py
+++ b/tidbcloudy/specification.py
@@ -366,8 +366,8 @@ def __repr__(self):
 
 class ProjectAWSCMEK(TiDBCloudyBase):
     __slots__ = ["_region", "_kms_arn"]
-    region: str = None
-    kms_arn: str = None
+    region: str = TiDBCloudyField(str)
+    kms_arn: str = TiDBCloudyField(str)
 
     def __repr__(self):
         return "<region={}, kms_arn={}>".format(