diff --git a/irc.go b/irc.go
index 4623472..1ea6ed7 100644
--- a/irc.go
+++ b/irc.go
@@ -198,4 +198,5 @@ type batch struct {
 	Type   string
 	Params []string
 	Outer  *batch // if not-nil, this batch is nested in Outer
+	Label  string
 }
diff --git a/upstream.go b/upstream.go
index a84f438..49ccbaf 100644
--- a/upstream.go
+++ b/upstream.go
@@ -3,6 +3,7 @@ package soju
 import (
 	"crypto/tls"
 	"encoding/base64"
+	"errors"
 	"fmt"
 	"io"
 	"net"
@@ -51,7 +52,9 @@ type upstreamConn struct {
 	caps       map[string]string
 	batches    map[string]batch
 
-	tagsSupported bool
+	tagsSupported   bool
+	labelsSupported bool
+	nextLabelId     uint64
 
 	saslClient  sasl.Client
 	saslStarted bool
@@ -127,6 +130,15 @@ func (uc *upstreamConn) forEachDownstream(f func(*downstreamConn)) {
 	})
 }
 
+func (uc *upstreamConn) forEachDownstreamById(id uint64, f func(*downstreamConn)) {
+	uc.forEachDownstream(func(dc *downstreamConn) {
+		if id != 0 && id != dc.id {
+			return
+		}
+		f(dc)
+	})
+}
+
 func (uc *upstreamConn) getChannel(name string) (*upstreamChannel, error) {
 	ch, ok := uc.channels[name]
 	if !ok {
@@ -152,6 +164,11 @@ func (uc *upstreamConn) parseMembershipPrefix(s string) (membership *membership,
 }
 
 func (uc *upstreamConn) handleMessage(msg *irc.Message) error {
+	var label string
+	if l, ok := msg.GetTag("label"); ok {
+		label = l
+	}
+
 	var msgBatch *batch
 	if batchName, ok := msg.GetTag("batch"); ok {
 		b, ok := uc.batches[batchName]
@@ -159,6 +176,21 @@ func (uc *upstreamConn) handleMessage(msg *irc.Message) error {
 			return fmt.Errorf("unexpected batch reference: batch was not defined: %q", batchName)
 		}
 		msgBatch = &b
+		if label == "" {
+			label = msgBatch.Label
+		}
+	}
+
+	var downstreamId uint64 = 0
+	if label != "" {
+		var labelOffset uint64
+		n, err := fmt.Sscanf(label, "sd-%d-%d", &downstreamId, &labelOffset)
+		if err == nil && n < 2 {
+			err = errors.New("not enough arguments")
+		}
+		if err != nil {
+			return fmt.Errorf("unexpected message label: invalid downstream reference for label %q: %v", label, err)
+		}
 	}
 
 	switch msg.Command {
@@ -204,7 +236,7 @@ func (uc *upstreamConn) handleMessage(msg *irc.Message) error {
 			}
 
 			requestCaps := make([]string, 0, 16)
-			for _, c := range []string{"message-tags", "batch"} {
+			for _, c := range []string{"message-tags", "batch", "labeled-response"} {
 				if _, ok := uc.caps[c]; ok {
 					requestCaps = append(requestCaps, c)
 				}
@@ -431,10 +463,15 @@ func (uc *upstreamConn) handleMessage(msg *irc.Message) error {
 			if err := parseMessageParams(msg, nil, &batchType); err != nil {
 				return err
 			}
+			label := label
+			if label == "" && msgBatch != nil {
+				label = msgBatch.Label
+			}
 			uc.batches[tag] = batch{
 				Type:   batchType,
 				Params: msg.Params[2:],
 				Outer:  msgBatch,
+				Label:  label,
 			}
 		} else if strings.HasPrefix(tag, "-") {
 			tag = tag[1:]
@@ -949,6 +986,8 @@ func (uc *upstreamConn) handleMessage(msg *irc.Message) error {
 		})
 	case "TAGMSG":
 		// TODO: relay to downstream connections that accept message-tags
+	case "ACK":
+		// Ignore
 	case irc.RPL_YOURHOST, irc.RPL_CREATED:
 		// Ignore
 	case irc.RPL_LUSERCLIENT, irc.RPL_LUSEROP, irc.RPL_LUSERUNKNOWN, irc.RPL_LUSERCHANNELS, irc.RPL_LUSERME:
@@ -1047,6 +1086,8 @@ func (uc *upstreamConn) handleCapAck(name string, ok bool) error {
 		})
 	case "message-tags":
 		uc.tagsSupported = ok
+	case "labeled-response":
+		uc.labelsSupported = ok
 	}
 	return nil
 }
@@ -1073,3 +1114,14 @@ func (uc *upstreamConn) readMessages(ch chan<- upstreamIncomingMessage) error {
 func (uc *upstreamConn) SendMessage(msg *irc.Message) {
 	uc.outgoing <- msg
 }
+
+func (uc *upstreamConn) SendMessageLabeled(dc *downstreamConn, msg *irc.Message) {
+	if uc.labelsSupported {
+		if msg.Tags == nil {
+			msg.Tags = make(map[string]irc.TagValue)
+		}
+		msg.Tags["label"] = irc.TagValue(fmt.Sprintf("sd-%d-%d", dc.id, uc.nextLabelId))
+		uc.nextLabelId++
+	}
+	uc.SendMessage(msg)
+}