diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0cdbc29..6fdb17b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -19,6 +19,12 @@ project adheres to [Semantic Versioning](http://semver.org/).
 
 # History
 
+## [[v4.0.1](https://github.com/terraform-aws-modules/terraform-aws-eks/compare/v4.0.0...v4.0.1)] - 2019-05-07]
+
+### Changed
+
+- Fix annoying typo: worker_group_xx vs worker_groups_xx (by @max-rocket-internet)
+
 ## [[v4.0.0](https://github.com/terraform-aws-modules/terraform-aws-eks/compare/v3.0.0...v4.0.0)] - 2019-05-07]
 
 ### Added
diff --git a/README.md b/README.md
index 61dc4d1..33cc7e7 100644
--- a/README.md
+++ b/README.md
@@ -148,11 +148,11 @@ MIT Licensed. See [LICENSE](https://github.com/terraform-aws-modules/terraform-a
 | worker\_create\_security\_group | Whether to create a security group for the workers or attach the workers to `worker_security_group_id`. | string | `"true"` | no |
 | worker\_group\_count | The number of maps contained within the worker_groups list. | string | `"1"` | no |
 | worker\_group\_launch\_template\_count | The number of maps contained within the worker_groups_launch_template list. | string | `"0"` | no |
-| worker\_group\_launch\_template\_mixed | A list of maps defining worker group configurations to be defined using AWS Launch Templates. See workers_group_defaults for valid keys. | list | `[ { "name": "default" } ]` | no |
-| worker\_group\_launch\_template\_mixed\_count | The number of maps contained within the worker_group_launch_template_mixed list. | string | `"0"` | no |
+| worker\_group\_launch\_template\_mixed\_count | The number of maps contained within the worker_groups_launch_template_mixed list. | string | `"0"` | no |
 | worker\_group\_tags | A map defining extra tags to be applied to the worker group ASG. | map | `{ "default": [] }` | no |
 | worker\_groups | A list of maps defining worker group configurations to be defined using AWS Launch Configurations. See workers_group_defaults for valid keys. | list | `[ { "name": "default" } ]` | no |
 | worker\_groups\_launch\_template | A list of maps defining worker group configurations to be defined using AWS Launch Templates. See workers_group_defaults for valid keys. | list | `[ { "name": "default" } ]` | no |
+| worker\_groups\_launch\_template\_mixed | A list of maps defining worker group configurations to be defined using AWS Launch Templates. See workers_group_defaults for valid keys. | list | `[ { "name": "default" } ]` | no |
 | worker\_security\_group\_id | If provided, all workers will be attached to this security group. If not given, a security group will be created with necessary ingres/egress to work with the EKS cluster. | string | `""` | no |
 | worker\_sg\_ingress\_from\_port | Minimum port number from which pods will accept communication. Must be changed to a lower value if some pods in your cluster will expose a port lower than 1025 (e.g. 22, 80, or 443). | string | `"1025"` | no |
 | workers\_additional\_policies | Additional policies to be added to workers | list | `[]` | no |
diff --git a/data.tf b/data.tf
index 91e6570..e1ec701 100644
--- a/data.tf
+++ b/data.tf
@@ -133,5 +133,5 @@ data "aws_iam_instance_profile" "custom_worker_group_launch_template_iam_instanc
 
 data "aws_iam_instance_profile" "custom_worker_group_launch_template_mixed_iam_instance_profile" {
   count = "${var.manage_worker_iam_resources ? 0 : var.worker_group_launch_template_mixed_count}"
-  name  = "${lookup(var.worker_group_launch_template_mixed[count.index], "iam_instance_profile_name", local.workers_group_defaults["iam_instance_profile_name"])}"
+  name  = "${lookup(var.worker_groups_launch_template_mixed[count.index], "iam_instance_profile_name", local.workers_group_defaults["iam_instance_profile_name"])}"
 }
diff --git a/variables.tf b/variables.tf
index c1c4529..fb769c4 100644
--- a/variables.tf
+++ b/variables.tf
@@ -132,7 +132,7 @@ variable "worker_groups_launch_template" {
   ]
 }
 
-variable "worker_group_launch_template_mixed" {
+variable "worker_groups_launch_template_mixed" {
   description = "A list of maps defining worker group configurations to be defined using AWS Launch Templates. See workers_group_defaults for valid keys."
   type        = "list"
 
@@ -144,7 +144,7 @@ variable "worker_group_launch_template_mixed" {
 }
 
 variable "worker_group_launch_template_mixed_count" {
-  description = "The number of maps contained within the worker_group_launch_template_mixed list."
+  description = "The number of maps contained within the worker_groups_launch_template_mixed list."
   type        = "string"
   default     = "0"
 }
diff --git a/version b/version
index 857572f..82f24fd 100644
--- a/version
+++ b/version
@@ -1 +1 @@
-v4.0.0
+v4.0.1
diff --git a/workers_launch_template_mixed.tf b/workers_launch_template_mixed.tf
index bac40b9..3222f61 100644
--- a/workers_launch_template_mixed.tf
+++ b/workers_launch_template_mixed.tf
@@ -2,63 +2,63 @@
 
 resource "aws_autoscaling_group" "workers_launch_template_mixed" {
   count                   = "${var.worker_group_launch_template_mixed_count}"
-  name_prefix             = "${aws_eks_cluster.this.name}-${lookup(var.worker_group_launch_template_mixed[count.index], "name", count.index)}"
-  desired_capacity        = "${lookup(var.worker_group_launch_template_mixed[count.index], "asg_desired_capacity", local.workers_group_defaults["asg_desired_capacity"])}"
-  max_size                = "${lookup(var.worker_group_launch_template_mixed[count.index], "asg_max_size", local.workers_group_defaults["asg_max_size"])}"
-  min_size                = "${lookup(var.worker_group_launch_template_mixed[count.index], "asg_min_size", local.workers_group_defaults["asg_min_size"])}"
-  force_delete            = "${lookup(var.worker_group_launch_template_mixed[count.index], "asg_force_delete", local.workers_group_defaults["asg_force_delete"])}"
-  target_group_arns       = ["${compact(split(",", coalesce(lookup(var.worker_group_launch_template_mixed[count.index], "target_group_arns", ""), local.workers_group_defaults["target_group_arns"])))}"]
-  service_linked_role_arn = "${lookup(var.worker_group_launch_template_mixed[count.index], "service_linked_role_arn", local.workers_group_defaults["service_linked_role_arn"])}"
-  vpc_zone_identifier     = ["${split(",", coalesce(lookup(var.worker_group_launch_template_mixed[count.index], "subnets", ""), local.workers_group_defaults["subnets"]))}"]
-  protect_from_scale_in   = "${lookup(var.worker_group_launch_template_mixed[count.index], "protect_from_scale_in", local.workers_group_defaults["protect_from_scale_in"])}"
-  suspended_processes     = ["${compact(split(",", coalesce(lookup(var.worker_group_launch_template_mixed[count.index], "suspended_processes", ""), local.workers_group_defaults["suspended_processes"])))}"]
-  enabled_metrics         = ["${compact(split(",", coalesce(lookup(var.worker_group_launch_template_mixed[count.index], "enabled_metrics", ""), local.workers_group_defaults["enabled_metrics"])))}"]
-  placement_group         = "${lookup(var.worker_group_launch_template_mixed[count.index], "placement_group", local.workers_group_defaults["placement_group"])}"
+  name_prefix             = "${aws_eks_cluster.this.name}-${lookup(var.worker_groups_launch_template_mixed[count.index], "name", count.index)}"
+  desired_capacity        = "${lookup(var.worker_groups_launch_template_mixed[count.index], "asg_desired_capacity", local.workers_group_defaults["asg_desired_capacity"])}"
+  max_size                = "${lookup(var.worker_groups_launch_template_mixed[count.index], "asg_max_size", local.workers_group_defaults["asg_max_size"])}"
+  min_size                = "${lookup(var.worker_groups_launch_template_mixed[count.index], "asg_min_size", local.workers_group_defaults["asg_min_size"])}"
+  force_delete            = "${lookup(var.worker_groups_launch_template_mixed[count.index], "asg_force_delete", local.workers_group_defaults["asg_force_delete"])}"
+  target_group_arns       = ["${compact(split(",", coalesce(lookup(var.worker_groups_launch_template_mixed[count.index], "target_group_arns", ""), local.workers_group_defaults["target_group_arns"])))}"]
+  service_linked_role_arn = "${lookup(var.worker_groups_launch_template_mixed[count.index], "service_linked_role_arn", local.workers_group_defaults["service_linked_role_arn"])}"
+  vpc_zone_identifier     = ["${split(",", coalesce(lookup(var.worker_groups_launch_template_mixed[count.index], "subnets", ""), local.workers_group_defaults["subnets"]))}"]
+  protect_from_scale_in   = "${lookup(var.worker_groups_launch_template_mixed[count.index], "protect_from_scale_in", local.workers_group_defaults["protect_from_scale_in"])}"
+  suspended_processes     = ["${compact(split(",", coalesce(lookup(var.worker_groups_launch_template_mixed[count.index], "suspended_processes", ""), local.workers_group_defaults["suspended_processes"])))}"]
+  enabled_metrics         = ["${compact(split(",", coalesce(lookup(var.worker_groups_launch_template_mixed[count.index], "enabled_metrics", ""), local.workers_group_defaults["enabled_metrics"])))}"]
+  placement_group         = "${lookup(var.worker_groups_launch_template_mixed[count.index], "placement_group", local.workers_group_defaults["placement_group"])}"
 
   mixed_instances_policy {
     instances_distribution {
-      on_demand_allocation_strategy            = "${lookup(var.worker_group_launch_template_mixed[count.index], "on_demand_allocation_strategy", local.workers_group_defaults["on_demand_allocation_strategy"])}"
-      on_demand_base_capacity                  = "${lookup(var.worker_group_launch_template_mixed[count.index], "on_demand_base_capacity", local.workers_group_defaults["on_demand_base_capacity"])}"
-      on_demand_percentage_above_base_capacity = "${lookup(var.worker_group_launch_template_mixed[count.index], "on_demand_percentage_above_base_capacity", local.workers_group_defaults["on_demand_percentage_above_base_capacity"])}"
-      spot_allocation_strategy                 = "${lookup(var.worker_group_launch_template_mixed[count.index], "spot_allocation_strategy", local.workers_group_defaults["spot_allocation_strategy"])}"
-      spot_instance_pools                      = "${lookup(var.worker_group_launch_template_mixed[count.index], "spot_instance_pools", local.workers_group_defaults["spot_instance_pools"])}"
-      spot_max_price                           = "${lookup(var.worker_group_launch_template_mixed[count.index], "spot_max_price", local.workers_group_defaults["spot_max_price"])}"
+      on_demand_allocation_strategy            = "${lookup(var.worker_groups_launch_template_mixed[count.index], "on_demand_allocation_strategy", local.workers_group_defaults["on_demand_allocation_strategy"])}"
+      on_demand_base_capacity                  = "${lookup(var.worker_groups_launch_template_mixed[count.index], "on_demand_base_capacity", local.workers_group_defaults["on_demand_base_capacity"])}"
+      on_demand_percentage_above_base_capacity = "${lookup(var.worker_groups_launch_template_mixed[count.index], "on_demand_percentage_above_base_capacity", local.workers_group_defaults["on_demand_percentage_above_base_capacity"])}"
+      spot_allocation_strategy                 = "${lookup(var.worker_groups_launch_template_mixed[count.index], "spot_allocation_strategy", local.workers_group_defaults["spot_allocation_strategy"])}"
+      spot_instance_pools                      = "${lookup(var.worker_groups_launch_template_mixed[count.index], "spot_instance_pools", local.workers_group_defaults["spot_instance_pools"])}"
+      spot_max_price                           = "${lookup(var.worker_groups_launch_template_mixed[count.index], "spot_max_price", local.workers_group_defaults["spot_max_price"])}"
     }
 
     launch_template {
       launch_template_specification {
         launch_template_id = "${element(aws_launch_template.workers_launch_template_mixed.*.id, count.index)}"
-        version            = "${lookup(var.worker_group_launch_template_mixed[count.index], "launch_template_version", local.workers_group_defaults["launch_template_version"])}"
+        version            = "${lookup(var.worker_groups_launch_template_mixed[count.index], "launch_template_version", local.workers_group_defaults["launch_template_version"])}"
       }
 
       override {
-        instance_type = "${lookup(var.worker_group_launch_template_mixed[count.index], "override_instance_type_1", local.workers_group_defaults["override_instance_type_1"])}"
+        instance_type = "${lookup(var.worker_groups_launch_template_mixed[count.index], "override_instance_type_1", local.workers_group_defaults["override_instance_type_1"])}"
       }
 
       override {
-        instance_type = "${lookup(var.worker_group_launch_template_mixed[count.index], "override_instance_type_2", local.workers_group_defaults["override_instance_type_2"])}"
+        instance_type = "${lookup(var.worker_groups_launch_template_mixed[count.index], "override_instance_type_2", local.workers_group_defaults["override_instance_type_2"])}"
       }
 
       override {
-        instance_type = "${lookup(var.worker_group_launch_template_mixed[count.index], "override_instance_type_3", local.workers_group_defaults["override_instance_type_3"])}"
+        instance_type = "${lookup(var.worker_groups_launch_template_mixed[count.index], "override_instance_type_3", local.workers_group_defaults["override_instance_type_3"])}"
       }
 
       override {
-        instance_type = "${lookup(var.worker_group_launch_template_mixed[count.index], "override_instance_type_4", local.workers_group_defaults["override_instance_type_4"])}"
+        instance_type = "${lookup(var.worker_groups_launch_template_mixed[count.index], "override_instance_type_4", local.workers_group_defaults["override_instance_type_4"])}"
       }
     }
   }
 
   tags = ["${concat(
     list(
-      map("key", "Name", "value", "${aws_eks_cluster.this.name}-${lookup(var.worker_group_launch_template_mixed[count.index], "name", count.index)}-eks_asg", "propagate_at_launch", true),
+      map("key", "Name", "value", "${aws_eks_cluster.this.name}-${lookup(var.worker_groups_launch_template_mixed[count.index], "name", count.index)}-eks_asg", "propagate_at_launch", true),
       map("key", "kubernetes.io/cluster/${aws_eks_cluster.this.name}", "value", "owned", "propagate_at_launch", true),
-      map("key", "k8s.io/cluster-autoscaler/${lookup(var.worker_group_launch_template_mixed[count.index], "autoscaling_enabled", local.workers_group_defaults["autoscaling_enabled"]) == 1 ? "enabled" : "disabled"  }", "value", "true", "propagate_at_launch", false),
+      map("key", "k8s.io/cluster-autoscaler/${lookup(var.worker_groups_launch_template_mixed[count.index], "autoscaling_enabled", local.workers_group_defaults["autoscaling_enabled"]) == 1 ? "enabled" : "disabled"  }", "value", "true", "propagate_at_launch", false),
       map("key", "k8s.io/cluster-autoscaler/${aws_eks_cluster.this.name}", "value", "", "propagate_at_launch", false),
-      map("key", "k8s.io/cluster-autoscaler/node-template/resources/ephemeral-storage", "value", "${lookup(var.worker_group_launch_template_mixed[count.index], "root_volume_size", local.workers_group_defaults["root_volume_size"])}Gi", "propagate_at_launch", false)
+      map("key", "k8s.io/cluster-autoscaler/node-template/resources/ephemeral-storage", "value", "${lookup(var.worker_groups_launch_template_mixed[count.index], "root_volume_size", local.workers_group_defaults["root_volume_size"])}Gi", "propagate_at_launch", false)
     ),
     local.asg_tags,
-    var.worker_group_tags[contains(keys(var.worker_group_tags), "${lookup(var.worker_group_launch_template_mixed[count.index], "name", count.index)}") ? "${lookup(var.worker_group_launch_template_mixed[count.index], "name", count.index)}" : "default"])
+    var.worker_group_tags[contains(keys(var.worker_group_tags), "${lookup(var.worker_groups_launch_template_mixed[count.index], "name", count.index)}") ? "${lookup(var.worker_groups_launch_template_mixed[count.index], "name", count.index)}" : "default"])
   }"]
 
   lifecycle {
@@ -69,42 +69,42 @@ resource "aws_autoscaling_group" "workers_launch_template_mixed" {
 
 resource "aws_launch_template" "workers_launch_template_mixed" {
   count       = "${var.worker_group_launch_template_mixed_count}"
-  name_prefix = "${aws_eks_cluster.this.name}-${lookup(var.worker_group_launch_template_mixed[count.index], "name", count.index)}"
+  name_prefix = "${aws_eks_cluster.this.name}-${lookup(var.worker_groups_launch_template_mixed[count.index], "name", count.index)}"
 
   network_interfaces {
-    associate_public_ip_address = "${lookup(var.worker_group_launch_template_mixed[count.index], "public_ip", local.workers_group_defaults["public_ip"])}"
-    delete_on_termination       = "${lookup(var.worker_group_launch_template_mixed[count.index], "eni_delete", local.workers_group_defaults["eni_delete"])}"
-    security_groups             = ["${local.worker_security_group_id}", "${var.worker_additional_security_group_ids}", "${compact(split(",",lookup(var.worker_group_launch_template_mixed[count.index],"additional_security_group_ids", local.workers_group_defaults["additional_security_group_ids"])))}"]
+    associate_public_ip_address = "${lookup(var.worker_groups_launch_template_mixed[count.index], "public_ip", local.workers_group_defaults["public_ip"])}"
+    delete_on_termination       = "${lookup(var.worker_groups_launch_template_mixed[count.index], "eni_delete", local.workers_group_defaults["eni_delete"])}"
+    security_groups             = ["${local.worker_security_group_id}", "${var.worker_additional_security_group_ids}", "${compact(split(",",lookup(var.worker_groups_launch_template_mixed[count.index],"additional_security_group_ids", local.workers_group_defaults["additional_security_group_ids"])))}"]
   }
 
   iam_instance_profile {
     name = "${element(coalescelist(aws_iam_instance_profile.workers_launch_template_mixed.*.name, data.aws_iam_instance_profile.custom_worker_group_launch_template_mixed_iam_instance_profile.*.name), count.index)}"
   }
 
-  image_id      = "${lookup(var.worker_group_launch_template_mixed[count.index], "ami_id", local.workers_group_defaults["ami_id"])}"
-  instance_type = "${lookup(var.worker_group_launch_template_mixed[count.index], "instance_type", local.workers_group_defaults["instance_type"])}"
-  key_name      = "${lookup(var.worker_group_launch_template_mixed[count.index], "key_name", local.workers_group_defaults["key_name"])}"
+  image_id      = "${lookup(var.worker_groups_launch_template_mixed[count.index], "ami_id", local.workers_group_defaults["ami_id"])}"
+  instance_type = "${lookup(var.worker_groups_launch_template_mixed[count.index], "instance_type", local.workers_group_defaults["instance_type"])}"
+  key_name      = "${lookup(var.worker_groups_launch_template_mixed[count.index], "key_name", local.workers_group_defaults["key_name"])}"
   user_data     = "${base64encode(element(data.template_file.workers_launch_template_mixed.*.rendered, count.index))}"
-  ebs_optimized = "${lookup(var.worker_group_launch_template_mixed[count.index], "ebs_optimized", lookup(local.ebs_optimized, lookup(var.worker_group_launch_template_mixed[count.index], "instance_type", local.workers_group_defaults["instance_type"]), false))}"
+  ebs_optimized = "${lookup(var.worker_groups_launch_template_mixed[count.index], "ebs_optimized", lookup(local.ebs_optimized, lookup(var.worker_groups_launch_template_mixed[count.index], "instance_type", local.workers_group_defaults["instance_type"]), false))}"
 
   monitoring {
-    enabled = "${lookup(var.worker_group_launch_template_mixed[count.index], "enable_monitoring", local.workers_group_defaults["enable_monitoring"])}"
+    enabled = "${lookup(var.worker_groups_launch_template_mixed[count.index], "enable_monitoring", local.workers_group_defaults["enable_monitoring"])}"
   }
 
   placement {
-    tenancy    = "${lookup(var.worker_group_launch_template_mixed[count.index], "launch_template_placement_tenancy", local.workers_group_defaults["launch_template_placement_tenancy"])}"
-    group_name = "${lookup(var.worker_group_launch_template_mixed[count.index], "launch_template_placement_group", local.workers_group_defaults["launch_template_placement_group"])}"
+    tenancy    = "${lookup(var.worker_groups_launch_template_mixed[count.index], "launch_template_placement_tenancy", local.workers_group_defaults["launch_template_placement_tenancy"])}"
+    group_name = "${lookup(var.worker_groups_launch_template_mixed[count.index], "launch_template_placement_group", local.workers_group_defaults["launch_template_placement_group"])}"
   }
 
   block_device_mappings {
-    device_name = "${lookup(var.worker_group_launch_template_mixed[count.index], "root_block_device_name", local.workers_group_defaults["root_block_device_name"])}"
+    device_name = "${lookup(var.worker_groups_launch_template_mixed[count.index], "root_block_device_name", local.workers_group_defaults["root_block_device_name"])}"
 
     ebs {
-      volume_size           = "${lookup(var.worker_group_launch_template_mixed[count.index], "root_volume_size", local.workers_group_defaults["root_volume_size"])}"
-      volume_type           = "${lookup(var.worker_group_launch_template_mixed[count.index], "root_volume_type", local.workers_group_defaults["root_volume_type"])}"
-      iops                  = "${lookup(var.worker_group_launch_template_mixed[count.index], "root_iops", local.workers_group_defaults["root_iops"])}"
-      encrypted             = "${lookup(var.worker_group_launch_template_mixed[count.index], "root_encrypted", local.workers_group_defaults["root_encrypted"])}"
-      kms_key_id            = "${lookup(var.worker_group_launch_template_mixed[count.index], "root_kms_key_id", local.workers_group_defaults["root_kms_key_id"])}"
+      volume_size           = "${lookup(var.worker_groups_launch_template_mixed[count.index], "root_volume_size", local.workers_group_defaults["root_volume_size"])}"
+      volume_type           = "${lookup(var.worker_groups_launch_template_mixed[count.index], "root_volume_type", local.workers_group_defaults["root_volume_type"])}"
+      iops                  = "${lookup(var.worker_groups_launch_template_mixed[count.index], "root_iops", local.workers_group_defaults["root_iops"])}"
+      encrypted             = "${lookup(var.worker_groups_launch_template_mixed[count.index], "root_encrypted", local.workers_group_defaults["root_encrypted"])}"
+      kms_key_id            = "${lookup(var.worker_groups_launch_template_mixed[count.index], "root_kms_key_id", local.workers_group_defaults["root_kms_key_id"])}"
       delete_on_termination = true
     }
   }
@@ -117,6 +117,6 @@ resource "aws_launch_template" "workers_launch_template_mixed" {
 resource "aws_iam_instance_profile" "workers_launch_template_mixed" {
   count       = "${var.worker_group_launch_template_mixed_count}"
   name_prefix = "${aws_eks_cluster.this.name}"
-  role        = "${lookup(var.worker_group_launch_template_mixed[count.index], "iam_role_id",  lookup(local.workers_group_defaults, "iam_role_id"))}"
+  role        = "${lookup(var.worker_groups_launch_template_mixed[count.index], "iam_role_id",  lookup(local.workers_group_defaults, "iam_role_id"))}"
   path        = "${var.iam_path}"
 }