diff --git a/firewall-production.tf b/firewall-production.tf
index bd0bb04..c9f0f91 100644
--- a/firewall-production.tf
+++ b/firewall-production.tf
@@ -94,10 +94,10 @@ resource "aws_networkfirewall_firewall" "default_firewall" {
   vpc_id              = aws_vpc.default.id
   subnet_mapping {
     count     = length(var.public_subnets_cidr)
-    subnet_id = element(var.public_subnets_cidr, count.index)
+    subnet_id = element(aws_subnet.public_subnet.*.id, count.index)
   }
   subnet_mapping {
     count     = length(var.private_subnets_cidr)
-    subnet_id = element(var.private_subnets_cidr, count.index)
+    subnet_id = element(aws_subnet.private_subnet.*.id, count.index)
   }
 }
\ No newline at end of file