Question (or bug?): Terraform false drift detection in task definition version

Really weird thing: “Terraform plan” reports drift for all task definitions, for instance:

~ task_definition = "arn:aws:ecs:us-east-1:xxxxxxxx:task-definition/my-service:4" -> "arn:aws:ecs:us-east-1:xxxxxxxx:task-definition/my-service:3"
I.e. Terrafrom wants to deploy the previous version of my task. But - both in the ECS cluster and in the Terrafrom state JSON I see the 4th version of my task definition. And obviously “3” isn’t hardcoded (version number is different for each service).

Any ideas?