diff --git a/sip/transaction_client_tx.go b/sip/transaction_client_tx.go
index 1d89ca7..b5a61d3 100644
--- a/sip/transaction_client_tx.go
+++ b/sip/transaction_client_tx.go
@@ -155,6 +155,11 @@ func (tx *ClientTx) ack() {
 	ack := newAckRequestNon2xx(tx.origin, resp, nil)
 	tx.fsmAck = ack // NOTE: this could be incorect property to use but it helps preventing loops in some cases
 
+	// https://github.com/emiago/sipgo/issues/168
+	// Destination can be FQDN and we do not want to resolve this.
+	// Still in case reliable connection, this ack will reuse same INVITE connection
+	ack.SetDestination(tx.origin.Destination())
+
 	err := tx.conn.WriteMsg(ack)
 	if err != nil {
 		tx.log.Error().
diff --git a/sip/transport_layer.go b/sip/transport_layer.go
index 96d5d78..5b2e851 100644
--- a/sip/transport_layer.go
+++ b/sip/transport_layer.go
@@ -313,6 +313,8 @@ func (l *TransportLayer) ClientRequestConnection(ctx context.Context, req *Reque
 		}
 
 		// Save destination in request to avoid repeated resolving
+		// This also solves problem where subsequent request like NON 2xx ACK can
+		// send on same destination without resolving again.
 		req.SetDestination(raddr.String())
 	}