diff --git a/main.tf b/main.tf
index ff687e490a1ff02a27cbcb4a113d7696898bd72b..37424a4ca2b431bd2a84664939361ece673a6255 100644
--- a/main.tf
+++ b/main.tf
@@ -72,8 +72,10 @@ module "create-ohpc-instance" {
     floating_ip_ohpc = module.floating-ip-address.ohpc_address
     ohpc_user =  var.ohpc_user
     ssh_private_key = var.ssh_private_key
-    vol_id = data.openstack_blockstorage_volume_v3.disk.id
-    vol_id2 = data.openstack_blockstorage_volume_v3.disk2.id
+    vol_ids = [
+      data.openstack_blockstorage_volume_v3.disk.id,
+      data.openstack_blockstorage_volume_v3.disk2.id,
+    ]
 }
 
 # runs the ood-instance module - creates ood instance using variables defined above