Missing attribute ecs.capability.gmsa

I am executing a windows container and have incorporated gMSA for authentication against domain resources.
When I pull the image and run directly on the host using the --security-opt "credentialspec=file://, the container executes and I'm able to reach the website hosted by the container.
When I attempt to execute using ECS and the GMSA security option in the task definition I receive the missing attribute ecs.capability.gmsa error when using the ecs-cli to check required attributes.

I'm unable to locate how to enable this capability in the container. ECS-Agent is 1.81, which I realize is not current. However when I spin up a new instance using the Windows 2016 ECS Optimized AMI, this is the version that is included.