diff --git a/debian/main.tf b/debian/main.tf
index 842bede..39f4cb1 100644
--- a/debian/main.tf
+++ b/debian/main.tf
@@ -23,5 +23,5 @@ module "tf_debian_vm" {
   bridge_name           = coalesce(var.bridge_name, module.invariants.bridge_name)
   ca_host               = coalesce(var.ca_host, module.invariants.ca_host)
   memory                = var.memory
-  data_disks            = var.data_disks
+  data_disk             = var.data_disk
 }
diff --git a/debian/variables.tf b/debian/variables.tf
index d631405..4e37c07 100644
--- a/debian/variables.tf
+++ b/debian/variables.tf
@@ -52,7 +52,7 @@ variable "memory" {
   default = 1024
 }
 
-variable "data_disks" {
-  type    = list(string)
-  default = []
+variable "data_disk" {
+  type    = string
+  default = null
 }