diff --git a/images/ubuntu/templates/variable.ubuntu.pkr.hcl b/images/ubuntu/templates/variable.ubuntu.pkr.hcl
index 05ba85877..e2c6aaf76 100644
--- a/images/ubuntu/templates/variable.ubuntu.pkr.hcl
+++ b/images/ubuntu/templates/variable.ubuntu.pkr.hcl
@@ -96,7 +96,7 @@ variable "private_virtual_network_with_public_ip" {
 }
 variable "os_disk_size_gb" {
   type    = number
-  default = 0
+  default = null
 }
 variable "source_image_version" {
   type    = string
diff --git a/images/windows/templates/variable.windows.pkr.hcl b/images/windows/templates/variable.windows.pkr.hcl
index daf69c66f..1605ce4a5 100644
--- a/images/windows/templates/variable.windows.pkr.hcl
+++ b/images/windows/templates/variable.windows.pkr.hcl
@@ -104,7 +104,7 @@ variable "private_virtual_network_with_public_ip" {
 }
 variable "os_disk_size_gb" {
   type    = number
-  default = 0
+  default = null
 }
 variable "source_image_version" {
   type    = string