I am trying to update my RDS engine as always

Hi LucasG,

The AllowMajorVersionUpgrade flag must be set to true before you will be able to upgrade to a new major version on your Amazon RDS cluster. It is not a required field in AWS CloudFormation templates, or the API or CLI ( --allow-major-version-upgrade). AWS will assume an implicit false if not provided. So to allow for an upgrade to occur if you are specifying a newer major version, you need to set this flag to TRUE. If you set the major version alone, then the request will fail with the error you are receiving. You can view the CloudFormation syntax for this field here.

References:

• AllowMajorVersionUpgrade
• Upgrading a DB instance engine version - Amazon RDS User Guide