diff --git a/debian/main.tf b/debian/main.tf
index 8cb5257..f556d30 100644
--- a/debian/main.tf
+++ b/debian/main.tf
@@ -127,7 +127,7 @@ resource "libvirt_domain" "debian" {
   }
 
   dynamic "disk" {
-    for_each = var.data_disk != null ? [1] : []
+    for_each = var.data_disk != "" ? [1] : []
 
     content {
       volume_id = var.data_disk