error_ebs_terraform

-------- vars.

variable "ebs_block_device"         { default = { device_name = "/dev/sdc" }
                                      type = "map"
                                    }                                  
-------- main.tf

resource "aws_launch_configuration" "LaunchConfig" {
  name_prefix = "lc-${var.product}-"
  image_id = "${var.ami_id}"
  instance_type = "${var.instance_type}"
  security_groups = ["${var.sg-ec2-id}"]
  iam_instance_profile = "${var.instance_profile}"
  key_name = "${var.key_pair}"
  ebs_block_device = ["${var.ebs_block_device}"]
  user_data = "${var.user_data}"
  lifecycle {
    create_before_destroy = true
  }
}


erro i get : ebs_block_device.0: expected object, got string