Macro Transform LanguageExtensions not working

[BourgoisMickael]

I can't get this code from the doc to deploy:

AWSTemplateFormatVersion: 2010-09-09
Transform: AWS::LanguageExtensions
Resources:
  Table:
    Type: AWS::DynamoDB::Table

Using Transform: AWS::LanguageExtensions always results in

User: arn:aws:iam::XXX:user/admin is not authorized to perform: cloudformation:CreateChangeSet on resource: arn:aws:cloudformation:us-east-1:aws:transform/LanguageExtensions because no resource-based policy allows the cloudformation:CreateChangeSet action

Note that the user has full access rights.