Packer build assume_role

I’m not able to use packer builder assume_role config…

I’m using the example provided in docs:

“type”: “amazon-ebs”,
“assume_role”: {
“role_arn” : “arn:aws:iam::ACCOUNT_ID:role/ROLE_NAME”,
“session_name”: “SESSION_NAME”,
“external_id” : “EXTERNAL_ID”

I replaced the ACCOUNT_ID and ROLE_NAME with appropriate settings and provided SESSION_NAME and EXTERNAL_ID

When I try and run packer build I get the following error:

Error: Failed to prepare build: “amazon-ebs”

1 error occurred:
* unknown configuration key: ‘“assume_role”’

Is assume_role supported with IAM instance roles?

Thx for your help!

Packer version?
any other OS details?