diff --git a/downstream.go b/downstream.go
index 98668dd..7a0b248 100644
--- a/downstream.go
+++ b/downstream.go
@@ -71,12 +71,12 @@ type downstreamConn struct {
 
 	negociatingCaps bool
 	capVersion      int
-	caps            map[string]bool
 
 	saslServer sasl.Server
 
 	lock        sync.Mutex
 	ourMessages map[*irc.Message]struct{}
+	caps        map[string]bool
 }
 
 func newDownstreamConn(srv *Server, netConn net.Conn, id uint64) *downstreamConn {
@@ -85,8 +85,8 @@ func newDownstreamConn(srv *Server, netConn net.Conn, id uint64) *downstreamConn
 		conn:          *newConn(srv, netConn, logger),
 		id:            id,
 		ringConsumers: make(map[*network]*RingConsumer),
-		caps:          make(map[string]bool),
 		ourMessages:   make(map[*irc.Message]struct{}),
+		caps:          make(map[string]bool),
 	}
 	dc.hostname = netConn.RemoteAddr().String()
 	if host, _, err := net.SplitHostPort(dc.hostname); err == nil {
@@ -209,8 +209,27 @@ func (dc *downstreamConn) readMessages(ch chan<- event) error {
 	return nil
 }
 
+func (dc *downstreamConn) getCap(name string) bool {
+	dc.lock.Lock()
+	defer dc.lock.Unlock()
+	return dc.caps[name]
+}
+
 func (dc *downstreamConn) SendMessage(msg *irc.Message) {
-	// TODO: strip tags if the client doesn't support them (see runNetwork)
+	if !dc.getCap("message-tags") {
+		msg = msg.Copy()
+		for name := range msg.Tags {
+			supported := false
+			switch name {
+			case "time":
+				supported = dc.getCap("server-time")
+			}
+			if !supported {
+				delete(msg.Tags, name)
+			}
+		}
+	}
+
 	dc.conn.SendMessage(msg)
 }
 
@@ -258,7 +277,7 @@ func (dc *downstreamConn) handleMessageUnregistered(msg *irc.Message) error {
 			return err
 		}
 	case "AUTHENTICATE":
-		if !dc.caps["sasl"] {
+		if !dc.getCap("sasl") {
 			return ircError{&irc.Message{
 				Command: irc.ERR_SASLFAIL,
 				Params:  []string{"*", "AUTHENTICATE requires the \"sasl\" capability to be enabled"},
@@ -399,9 +418,11 @@ func (dc *downstreamConn) handleCapCommand(cmd string, args []string) error {
 		}
 	case "LIST":
 		var caps []string
+		dc.lock.Lock()
 		for name := range dc.caps {
 			caps = append(caps, name)
 		}
+		dc.lock.Unlock()
 
 		// TODO: multi-line replies
 		dc.SendMessage(&irc.Message{
@@ -419,6 +440,7 @@ func (dc *downstreamConn) handleCapCommand(cmd string, args []string) error {
 
 		caps := strings.Fields(args[0])
 		ack := true
+		dc.lock.Lock()
 		for _, name := range caps {
 			name = strings.ToLower(name)
 			enable := !strings.HasPrefix(name, "-")
@@ -438,6 +460,7 @@ func (dc *downstreamConn) handleCapCommand(cmd string, args []string) error {
 				ack = false
 			}
 		}
+		dc.lock.Unlock()
 
 		reply := "NAK"
 		if ack {
@@ -663,11 +686,6 @@ func (dc *downstreamConn) runNetwork(net *network, loadHistory bool) {
 		}
 	}
 
-	// TODO: can't be enabled/disabled on-the-fly
-	msgTagsEnabled := dc.caps["message-tags"]
-	serverTimeEnabled := dc.caps["server-time"]
-	echoMessageEnabled := dc.caps["echo-message"]
-
 	consumer, ch := net.ring.NewConsumer(seqPtr)
 
 	if _, ok := dc.ringConsumers[net]; ok {
@@ -693,7 +711,7 @@ func (dc *downstreamConn) runNetwork(net *network, loadHistory bool) {
 				_, ours := dc.ourMessages[msg]
 				delete(dc.ourMessages, msg)
 				dc.lock.Unlock()
-				if ours && !echoMessageEnabled {
+				if ours && !dc.getCap("echo-message") {
 					// The message comes from our connection, don't echo it
 					// back
 					consumer.Consume()
@@ -709,19 +727,6 @@ func (dc *downstreamConn) runNetwork(net *network, loadHistory bool) {
 					panic("expected to consume a PRIVMSG message")
 				}
 
-				if !msgTagsEnabled {
-					for name := range msg.Tags {
-						supported := false
-						switch name {
-						case "time":
-							supported = serverTimeEnabled
-						}
-						if !supported {
-							delete(msg.Tags, name)
-						}
-					}
-				}
-
 				dc.SendMessage(msg)
 				consumer.Consume()
 			}
diff --git a/logger.go b/logger.go
index ab8f15e..43b3eda 100644
--- a/logger.go
+++ b/logger.go
@@ -31,6 +31,8 @@ func (ml *messageLogger) Append(msg *irc.Message) error {
 		return nil
 	}
 
+	// TODO: parse time from msg.Tags["time"], if available
+
 	// TODO: enforce maximum open file handles (LRU cache of file handles)
 	// TODO: handle non-monotonic clock behaviour
 	now := time.Now()
diff --git a/upstream.go b/upstream.go
index f21740d..d9f358b 100644
--- a/upstream.go
+++ b/upstream.go
@@ -245,6 +245,10 @@ func (uc *upstreamConn) handleMessage(msg *irc.Message) error {
 		}
 	}
 
+	if _, ok := msg.Tags["time"]; !ok {
+		msg.Tags["time"] = irc.TagValue(time.Now().Format(serverTimeLayout))
+	}
+
 	switch msg.Command {
 	case "PING":
 		uc.SendMessage(&irc.Message{
@@ -1149,10 +1153,6 @@ func (uc *upstreamConn) handleMessage(msg *irc.Message) error {
 			break
 		}
 
-		if _, ok := msg.Tags["time"]; !ok {
-			msg.Tags["time"] = irc.TagValue(time.Now().Format(serverTimeLayout))
-		}
-
 		target := nick
 		if nick == uc.nick {
 			target = msg.Prefix.Name