diff --git a/google-cloud/container-linux/kubernetes/variables.tf b/google-cloud/container-linux/kubernetes/variables.tf
index abcaec84..aff3f0e8 100644
--- a/google-cloud/container-linux/kubernetes/variables.tf
+++ b/google-cloud/container-linux/kubernetes/variables.tf
@@ -34,13 +34,13 @@ variable "worker_count" {
   description = "Number of workers"
 }
 
-variable controller_type {
+variable "controller_type" {
   type        = "string"
   default     = "n1-standard-1"
   description = "Machine type for controllers (see `gcloud compute machine-types list`)"
 }
 
-variable worker_type {
+variable "worker_type" {
   type        = "string"
   default     = "n1-standard-1"
   description = "Machine type for controllers (see `gcloud compute machine-types list`)"