diff --git a/sg_https_only/variables.tf b/sg_https_only/variables.tf
index 0175c5a..058509e 100644
--- a/sg_https_only/variables.tf
+++ b/sg_https_only/variables.tf
@@ -9,7 +9,8 @@ variable "vpc_id" {
 
 variable "source_cidr_block" {
   description = "The source CIDR block to allow traffic from"
-  default     = "0.0.0.0/0"
+  default     = ["0.0.0.0/0"]
+  type        = "list"
 }
 
 variable "tags" {