diff --git a/data/data/aws/main.tf b/data/data/aws/main.tf
index f0fc7674747..f6d7db44e6b 100644
--- a/data/data/aws/main.tf
+++ b/data/data/aws/main.tf
@@ -93,10 +93,6 @@ module "vpc" {
   external_worker_subnet_ids = "${compact(var.tectonic_aws_external_worker_subnet_ids)}"
   extra_tags                 = "${var.tectonic_aws_extra_tags}"
 
-  // empty map subnet_configs will have the vpc module creating subnets in all availabile AZs
-  new_master_subnet_configs = "${var.tectonic_aws_master_custom_subnets}"
-  new_worker_subnet_configs = "${var.tectonic_aws_worker_custom_subnets}"
-
   private_master_endpoints = "${local.private_endpoints}"
   public_master_endpoints  = "${local.public_endpoints}"
 }
diff --git a/data/data/aws/variables-aws.tf b/data/data/aws/variables-aws.tf
index 615e9a19045..76bbc70cb7c 100644
--- a/data/data/aws/variables-aws.tf
+++ b/data/data/aws/variables-aws.tf
@@ -171,29 +171,6 @@ Ignored if the volume type is not io1.
 EOF
 }
 
-variable "tectonic_aws_master_custom_subnets" {
-  type    = "map"
-  default = {}
-
-  description = <<EOF
-(optional) This configures master availability zones and their corresponding subnet CIDRs directly.
-
-Example:
-`{ eu-west-1a = "10.0.0.0/20", eu-west-1b = "10.0.16.0/20" }`
-EOF
-}
-
-variable "tectonic_aws_worker_custom_subnets" {
-  type    = "map"
-  default = {}
-
-  description = <<EOF
-(optional) This configures worker availability zones and their corresponding subnet CIDRs directly.
-
-Example: `{ eu-west-1a = "10.0.64.0/20", eu-west-1b = "10.0.80.0/20" }`
-EOF
-}
-
 variable "tectonic_aws_region" {
   type        = "string"
   description = "The target AWS region for the cluster."
diff --git a/data/data/aws/vpc/common.tf b/data/data/aws/vpc/common.tf
index cc02009bcab..f8a9b66bc72 100644
--- a/data/data/aws/vpc/common.tf
+++ b/data/data/aws/vpc/common.tf
@@ -11,8 +11,8 @@ locals {
   external_vpc_mode = "${var.external_vpc_id != ""}"
 
   // List of possible AZs for each type of subnet
-  new_worker_subnet_azs = ["${coalescelist(keys(var.new_worker_subnet_configs), data.aws_availability_zones.azs.names)}"]
-  new_master_subnet_azs = ["${coalescelist(keys(var.new_master_subnet_configs), data.aws_availability_zones.azs.names)}"]
+  new_worker_subnet_azs = ["${data.aws_availability_zones.azs.names}"]
+  new_master_subnet_azs = ["${data.aws_availability_zones.azs.names}"]
 
   // How many AZs to create worker and master subnets in (always zero if external_vpc_mode)
   new_worker_az_count = "${local.external_vpc_mode ? 0 : length(local.new_worker_subnet_azs)}"
diff --git a/data/data/aws/vpc/variables.tf b/data/data/aws/vpc/variables.tf
index 4b3aa66e534..c518b6ce33a 100644
--- a/data/data/aws/vpc/variables.tf
+++ b/data/data/aws/vpc/variables.tf
@@ -32,16 +32,6 @@ variable "extra_tags" {
   default     = {}
 }
 
-variable "new_master_subnet_configs" {
-  description = "{az_name = new_subnet_cidr}: Empty map means create new subnets in all availability zones in region with generated cidrs"
-  type        = "map"
-}
-
-variable "new_worker_subnet_configs" {
-  description = "{az_name = new_subnet_cidr}: Empty map means create new subnets in all availability zones in region with generated cidrs"
-  type        = "map"
-}
-
 variable "private_master_endpoints" {
   description = "If set to true, private-facing ingress resources are created."
   default     = true
diff --git a/data/data/aws/vpc/vpc-private.tf b/data/data/aws/vpc/vpc-private.tf
index d55eb0e739a..b07c729cb64 100644
--- a/data/data/aws/vpc/vpc-private.tf
+++ b/data/data/aws/vpc/vpc-private.tf
@@ -22,10 +22,7 @@ resource "aws_subnet" "worker_subnet" {
 
   vpc_id = "${data.aws_vpc.cluster_vpc.id}"
 
-  cidr_block = "${lookup(var.new_worker_subnet_configs,
-    local.new_worker_subnet_azs[count.index],
-    cidrsubnet(local.new_worker_cidr_range, 3, count.index),
-  )}"
+  cidr_block = "${cidrsubnet(local.new_worker_cidr_range, 3, count.index)}"
 
   availability_zone = "${local.new_worker_subnet_azs[count.index]}"
 
diff --git a/data/data/aws/vpc/vpc-public.tf b/data/data/aws/vpc/vpc-public.tf
index 48595002280..9db13c5bb4e 100644
--- a/data/data/aws/vpc/vpc-public.tf
+++ b/data/data/aws/vpc/vpc-public.tf
@@ -37,10 +37,7 @@ resource "aws_subnet" "master_subnet" {
   count  = "${local.new_master_az_count}"
   vpc_id = "${data.aws_vpc.cluster_vpc.id}"
 
-  cidr_block = "${lookup(var.new_master_subnet_configs,
-    local.new_master_subnet_azs[count.index],
-    cidrsubnet(local.new_master_cidr_range, 3, count.index),
-  )}"
+  cidr_block = "${cidrsubnet(local.new_master_cidr_range, 3, count.index)}"
 
   availability_zone = "${local.new_master_subnet_azs[count.index]}"
 
diff --git a/pkg/tfvars/aws/aws.go b/pkg/tfvars/aws/aws.go
index 24de057bcdb..e3412779e4f 100644
--- a/pkg/tfvars/aws/aws.go
+++ b/pkg/tfvars/aws/aws.go
@@ -39,10 +39,9 @@ type External struct {
 
 // Master converts master related config.
 type Master struct {
-	CustomSubnets    map[string]string `json:"tectonic_aws_master_custom_subnets,omitempty"`
-	EC2Type          string            `json:"tectonic_aws_master_ec2_type,omitempty"`
-	ExtraSGIDs       []string          `json:"tectonic_aws_master_extra_sg_ids,omitempty"`
-	IAMRoleName      string            `json:"tectonic_aws_master_iam_role_name,omitempty"`
+	EC2Type          string   `json:"tectonic_aws_master_ec2_type,omitempty"`
+	ExtraSGIDs       []string `json:"tectonic_aws_master_extra_sg_ids,omitempty"`
+	IAMRoleName      string   `json:"tectonic_aws_master_iam_role_name,omitempty"`
 	MasterRootVolume `json:",inline"`
 }
 
@@ -55,11 +54,10 @@ type MasterRootVolume struct {
 
 // Worker converts worker related config.
 type Worker struct {
-	CustomSubnets    map[string]string `json:"tectonic_aws_worker_custom_subnets,omitempty"`
-	EC2Type          string            `json:"tectonic_aws_worker_ec2_type,omitempty"`
-	ExtraSGIDs       []string          `json:"tectonic_aws_worker_extra_sg_ids,omitempty"`
-	IAMRoleName      string            `json:"tectonic_aws_worker_iam_role_name,omitempty"`
-	LoadBalancers    []string          `json:"tectonic_aws_worker_load_balancers,omitempty"`
+	EC2Type          string   `json:"tectonic_aws_worker_ec2_type,omitempty"`
+	ExtraSGIDs       []string `json:"tectonic_aws_worker_extra_sg_ids,omitempty"`
+	IAMRoleName      string   `json:"tectonic_aws_worker_iam_role_name,omitempty"`
+	LoadBalancers    []string `json:"tectonic_aws_worker_load_balancers,omitempty"`
 	WorkerRootVolume `json:",inline"`
 }