diff --git a/upstream.go b/upstream.go
index 56ca018..cf49c57 100644
--- a/upstream.go
+++ b/upstream.go
@@ -298,40 +298,16 @@ func (uc *upstreamConn) handleMessage(msg *irc.Message) error {
 			if len(subParams) < 1 {
 				return newNeedMoreParamsError(msg.Command)
 			}
-			caps := strings.Fields(subParams[len(subParams)-1])
+			caps := subParams[len(subParams)-1]
 			more := len(subParams) >= 2 && msg.Params[len(subParams)-2] == "*"
 
-			for _, s := range caps {
-				kv := strings.SplitN(s, "=", 2)
-				k := strings.ToLower(kv[0])
-				var v string
-				if len(kv) == 2 {
-					v = kv[1]
-				}
-				uc.supportedCaps[k] = v
-			}
+			uc.handleSupportedCaps(caps)
 
 			if more {
 				break // wait to receive all capabilities
 			}
 
-			requestCaps := make([]string, 0, 16)
-			for _, c := range []string{"message-tags", "batch", "labeled-response", "server-time", "away-notify"} {
-				if _, ok := uc.supportedCaps[c]; ok {
-					requestCaps = append(requestCaps, c)
-				}
-			}
-
-			if uc.requestSASL() {
-				requestCaps = append(requestCaps, "sasl")
-			}
-
-			if len(requestCaps) > 0 {
-				uc.SendMessage(&irc.Message{
-					Command: "CAP",
-					Params:  []string{"REQ", strings.Join(requestCaps, " ")},
-				})
-			}
+			uc.requestCaps()
 
 			if uc.requestSASL() {
 				break // we'll send CAP END after authentication is completed
@@ -359,6 +335,34 @@ func (uc *upstreamConn) handleMessage(msg *irc.Message) error {
 					Params:  []string{"END"},
 				})
 			}
+
+			if uc.registered {
+				uc.forEachDownstream(func(dc *downstreamConn) {
+					dc.updateSupportedCaps()
+				})
+			}
+		case "NEW":
+			if len(subParams) < 1 {
+				return newNeedMoreParamsError(msg.Command)
+			}
+			uc.handleSupportedCaps(subParams[0])
+			uc.requestCaps()
+		case "DEL":
+			if len(subParams) < 1 {
+				return newNeedMoreParamsError(msg.Command)
+			}
+			caps := strings.Fields(subParams[0])
+
+			for _, c := range caps {
+				delete(uc.supportedCaps, c)
+				delete(uc.caps, c)
+			}
+
+			if uc.registered {
+				uc.forEachDownstream(func(dc *downstreamConn) {
+					dc.updateSupportedCaps()
+				})
+			}
 		default:
 			uc.logger.Printf("unhandled message: %v", msg)
 		}
@@ -1190,6 +1194,39 @@ func (uc *upstreamConn) handleMessage(msg *irc.Message) error {
 	return nil
 }
 
+func (uc *upstreamConn) handleSupportedCaps(capsStr string) {
+	caps := strings.Fields(capsStr)
+	for _, s := range caps {
+		kv := strings.SplitN(s, "=", 2)
+		k := strings.ToLower(kv[0])
+		var v string
+		if len(kv) == 2 {
+			v = kv[1]
+		}
+		uc.supportedCaps[k] = v
+	}
+}
+
+func (uc *upstreamConn) requestCaps() {
+	var requestCaps []string
+	for _, c := range []string{"message-tags", "batch", "labeled-response", "server-time", "away-notify"} {
+		if _, ok := uc.supportedCaps[c]; ok && !uc.caps[c] {
+			requestCaps = append(requestCaps, c)
+		}
+	}
+
+	if uc.requestSASL() && !uc.caps["sasl"] {
+		requestCaps = append(requestCaps, "sasl")
+	}
+
+	if len(requestCaps) > 0 {
+		uc.SendMessage(&irc.Message{
+			Command: "CAP",
+			Params:  []string{"REQ", strings.Join(requestCaps, " ")},
+		})
+	}
+}
+
 func splitSpace(s string) []string {
 	return strings.FieldsFunc(s, func(r rune) bool {
 		return r == ' '