diff --git a/command/agent/dns.go b/command/agent/dns.go
index 15378f58c..4244f63f8 100644
--- a/command/agent/dns.go
+++ b/command/agent/dns.go
@@ -194,6 +194,8 @@ func (d *DNSServer) handlePtr(resp dns.ResponseWriter, req *dns.Msg) {
 	}
 	var out structs.IndexedNodes
 
+	// TODO: Replace ListNodes with an internal RPC that can do the filter
+	// server side to avoid transfering the entire node list.
 	if err := d.agent.RPC("Catalog.ListNodes", &args, &out); err == nil {
 		for _, n := range out.Nodes {
 			arpa, _ := dns.ReverseAddr(n.Address)