Environment variables for credentials are not working

I am trying to use environment variables for credentials, I am able to inject and show the environment variables in a post install script, but codedeploy plugin is not able to use them, showing the following error:
is not authorized to perform: codedeploy:ListApplications on resource.. (Service: AmazonCodeDeploy; Status Code: 400; Error Code: AccessDeniedException; Request ID: ..)

I does work when I explicitly use the key id and access key on the form.

I am using 1.8 version of the plugin I am not sure if this is has been fixed on 1.9 looking at the changes appear that is not. In any case I will try the latest plugin later and will update this.