diff --git a/modules/subnet-group/README.md b/modules/subnet-group/README.md
index f21ad1a..44309eb 100644
--- a/modules/subnet-group/README.md
+++ b/modules/subnet-group/README.md
@@ -53,7 +53,7 @@ This module creates following resources.
 | Name | Description | Type | Default | Required |
 |------|-------------|------|---------|:--------:|
 | <a name="input_name"></a> [name](#input\_name) | (Required) The name of the subnet group. | `string` | n/a | yes |
-| <a name="input_subnets"></a> [subnets](#input\_subnets) | (Required) A configuration of subnets to create in the subnet group. Each block of `subnets` as defined below.<br>    (Optional) `type` - The type of subnet. Valid values are `DUALSTACK` and `IPV6`. Defaults to `DUALSTACK`.<br>    (Optional) `availability_zone` - The availability zone of the subnet. If the value of `availability_zone` and `availability_zone_id` are both not provided, the subnet will be created in random availability zone.<br>    (Optional) `availability_zone_id` - The availability zone ID of the subnet. If the value of `availability_zone` and `availability_zone_id` are both not provided, the subnet will be created in random availability zone. | <pre>map(object({<br>    type = optional(string, "DUALSTACK")<br><br>    availability_zone    = optional(string)<br>    availability_zone_id = optional(string)<br><br>    ipv4_cidr = optional(string)<br>    ipv6_cidr = optional(string)<br>  }))</pre> | n/a | yes |
+| <a name="input_subnets"></a> [subnets](#input\_subnets) | (Required) A configuration of subnets to create in the subnet group. Each block of `subnets` as defined below.<br>    (Optional) `type` - The type of subnet. Valid values are `DUALSTACK` and `IPV6`. Defaults to `DUALSTACK`.<br>    (Optional) `availability_zone` - The availability zone of the subnet. If the value of `availability_zone` and `availability_zone_id` are both not provided, the subnet will be created in random availability zone.<br>    (Optional) `availability_zone_id` - The availability zone ID of the subnet. If the value of `availability_zone` and `availability_zone_id` are both not provided, the subnet will be created in random availability zone.<br>    (Optional) `ipv4_cidr` - The IPv4 CIDR block for the subnet.<br>    (Optional) `ipv6_cidr` - The IPv6 network range for the subnet, in CIDR notation. The subnet size must use a /64 prefix length. | <pre>map(object({<br>    type = optional(string, "DUALSTACK")<br><br>    availability_zone    = optional(string)<br>    availability_zone_id = optional(string)<br><br>    ipv4_cidr = optional(string)<br>    ipv6_cidr = optional(string)<br>  }))</pre> | n/a | yes |
 | <a name="input_vpc_id"></a> [vpc\_id](#input\_vpc\_id) | (Required) The ID of the VPC which the subnet group belongs to. | `string` | n/a | yes |
 | <a name="input_customer_owned_ipv4_address_assignment"></a> [customer\_owned\_ipv4\_address\_assignment](#input\_customer\_owned\_ipv4\_address\_assignment) | (Optional) A configuration for Customer-owned IPv4 address assignment. `customer_owned_ipv4_address_assignment` as defined below.<br>    (Optional) `enabled` - Whether to automatically request a Customer-owned IPv4 address for a new network interface in this subnet. Defaults to `false`.<br>    (Optional) `outpost` - The Amazon Resource Name (ARN) of the Outpost.<br>    (Optional) `pool` - The customer owned IPv4 address pool. | <pre>object({<br>    enabled = optional(bool, false)<br>    outpost = optional(string)<br>    pool    = optional(string)<br>  })</pre> | `{}` | no |
 | <a name="input_dax_subnet_group"></a> [dax\_subnet\_group](#input\_dax\_subnet\_group) | (Optional) A configuration of DAX Subnet Group. `dax_subnet_group` as defined below.<br>    (Optional) `enabled` - Whether to create DAX Subnet Group. Defaults to `false`.<br>    (Optional) `name` - The name of the DAX Subnet Group. If not provided, the value of `name` will be used.<br>    (Optional) `description` - The description of the DAX Subnet Group. | <pre>object({<br>    enabled     = optional(bool, false)<br>    name        = optional(string)<br>    description = optional(string, "Managed by Terraform.")<br>  })</pre> | `{}` | no |
diff --git a/modules/subnet-group/variables.tf b/modules/subnet-group/variables.tf
index 3fe912a..aa12dca 100644
--- a/modules/subnet-group/variables.tf
+++ b/modules/subnet-group/variables.tf
@@ -16,6 +16,8 @@ variable "subnets" {
     (Optional) `type` - The type of subnet. Valid values are `DUALSTACK` and `IPV6`. Defaults to `DUALSTACK`.
     (Optional) `availability_zone` - The availability zone of the subnet. If the value of `availability_zone` and `availability_zone_id` are both not provided, the subnet will be created in random availability zone.
     (Optional) `availability_zone_id` - The availability zone ID of the subnet. If the value of `availability_zone` and `availability_zone_id` are both not provided, the subnet will be created in random availability zone.
+    (Optional) `ipv4_cidr` - The IPv4 CIDR block for the subnet.
+    (Optional) `ipv6_cidr` - The IPv6 network range for the subnet, in CIDR notation. The subnet size must use a /64 prefix length.
   EOF
   type = map(object({
     type = optional(string, "DUALSTACK")