diff --git a/terraform/infrastructure/iam/gcp/variables.tf b/terraform/infrastructure/iam/gcp/variables.tf
index b1895f0fc..37dc35144 100644
--- a/terraform/infrastructure/iam/gcp/variables.tf
+++ b/terraform/infrastructure/iam/gcp/variables.tf
@@ -5,6 +5,7 @@ variable "project_id" {
 
 variable "service_account_id" {
   type        = string
+  default     = null
   description = "[DEPRECATED use var.name_prefix] ID for the service account being created. Must match ^[a-z](?:[-a-z0-9]{4,28}[a-z0-9])$."
 }