diff --git a/nacl-rules/outputs.tf b/nacl-rules/outputs.tf
index 81b617e..3ecd2b3 100644
--- a/nacl-rules/outputs.tf
+++ b/nacl-rules/outputs.tf
@@ -5,7 +5,7 @@ output "info" {
     rule_count        = length(local.r4)
     first_rule_number = local.rule_number
     last_rule_number  = local.r5
-    next_rule_number  = local.r5 + local.rule_increment
+    next_rule_number  = local.r5 != null ? local.r5 + local.rule_increment : null
     rule_increment    = local.rule_increment
     cidrs             = local.cidr_blocks
     rules             = local.rules