Can't associate the 100.64.0.0/10 range as a secondary range to VPC with terraform

Terraform Providers AWS
1 
resource "aws_vpc_ipv4_cidr_block_association" "eks_vpc_secondary_cidr" {
  vpc_id = module.eks-vpc.vpc_id
  cidr_block = "100.64.0.0/10"
}

Error: expected "cidr_block" to contain a network Value with between 16 and 28 significant bits, got: 10

I’m using terraform “0.13.5” and aws provider “3.16.0”,

As far as I know “100.64.0.0/10” is a perfectly valid secondary CIDR for VPC and I have it configured it in the past (via the AWS console). It’s is used frequently when setting up EKS with CNI custom networking (where the pods are given IPs in the 100.64.0.0/10 range).

See Amazon EKS now supports additional VPC CIDR blocks

2

It’s the same with terraform 0.15.4 and aws provider 3.42.0 which are the lastest versions now (2021-05-31)

3

I filled a GitHub issue 19595.