diff --git a/cesnet-mcc/terraform/vms.tf b/cesnet-mcc/terraform/vms.tf
index 7837a72b3a4fad7d2f4d8e80a7ddf70f693937f8..4cb2bd3b3c177266aba723254bce0ec588a2dd24 100644
--- a/cesnet-mcc/terraform/vms.tf
+++ b/cesnet-mcc/terraform/vms.tf
@@ -27,6 +27,7 @@ resource "openstack_compute_secgroup_v2" "ping" {
   rule {
     from_port   = 128
     to_port     = 0
+    # initial installation (bug in terraform): ip_protocol = "icmp"
     ip_protocol = "ipv6-icmp"
     cidr        = "::/0"
   }