diff --git a/irc/caps/set.go b/irc/caps/set.go
index 31d4c98d..c33f6ecb 100644
--- a/irc/caps/set.go
+++ b/irc/caps/set.go
@@ -89,12 +89,15 @@ func (s *Set) Empty() bool {
 	return utils.BitsetEmpty(s[:])
 }
 
-const maxPayloadLength = 440
+const defaultMaxPayloadLength = 450
 
 // Strings returns all of our enabled capabilities as a slice of strings.
-func (s *Set) Strings(version Version, values Values) (result []string) {
+func (s *Set) Strings(version Version, values Values, maxLen int) (result []string) {
+	if maxLen == 0 {
+		maxLen = defaultMaxPayloadLength
+	}
 	var t utils.TokenLineBuilder
-	t.Initialize(maxPayloadLength, " ")
+	t.Initialize(maxLen, " ")
 
 	var capab Capability
 	asSlice := s[:]
diff --git a/irc/caps/set_test.go b/irc/caps/set_test.go
index 7ed909bd..dae983a0 100644
--- a/irc/caps/set_test.go
+++ b/irc/caps/set_test.go
@@ -47,13 +47,13 @@ func TestSets(t *testing.T) {
 	values := make(Values)
 	values[InviteNotify] = "invitemepls"
 
-	actualCap301ValuesString := s1.Strings(Cap301, values)
+	actualCap301ValuesString := s1.Strings(Cap301, values, 0)
 	expectedCap301ValuesString := []string{"invite-notify userhost-in-names"}
 	if !reflect.DeepEqual(actualCap301ValuesString, expectedCap301ValuesString) {
 		t.Errorf("Generated Cap301 values string [%v] did not match expected values string [%v]", actualCap301ValuesString, expectedCap301ValuesString)
 	}
 
-	actualCap302ValuesString := s1.Strings(Cap302, values)
+	actualCap302ValuesString := s1.Strings(Cap302, values, 0)
 	expectedCap302ValuesString := []string{"invite-notify=invitemepls userhost-in-names"}
 	if !reflect.DeepEqual(actualCap302ValuesString, expectedCap302ValuesString) {
 		t.Errorf("Generated Cap302 values string [%s] did not match expected values string [%s]", actualCap302ValuesString, expectedCap302ValuesString)
diff --git a/irc/handlers.go b/irc/handlers.go
index e5ac2a5e..6a073b12 100644
--- a/irc/handlers.go
+++ b/irc/handlers.go
@@ -569,9 +569,14 @@ func capHandler(server *Server, client *Client, msg ircmsg.IrcMessage, rb *Respo
 
 	sendCapLines := func(cset *caps.Set, values caps.Values) {
 		version := rb.session.capVersion
-		capLines := cset.Strings(version, values)
-		// weechat 1.4 has a bug here where it won't accept the CAP reply unless it contains
-		// the server.name source:
+		// we're working around two bugs:
+		// 1. weechat 1.4 won't accept the CAP reply unless it contains the server.name source
+		// 2. old versions of Kiwi and The Lounge can't parse multiline CAP LS 302 (#661),
+		// so try as hard as possible to get the response to fit on one line.
+		// :server.name CAP * LS * :<tokens>
+		// 1           7         4
+		maxLen := 510 - 1 - len(server.name) - 7 - len(subCommand) - 4
+		capLines := cset.Strings(version, values, maxLen)
 		for i, capStr := range capLines {
 			if version >= caps.Cap302 && i < len(capLines)-1 {
 				rb.Add(nil, server.name, "CAP", details.nick, subCommand, "*", capStr)
diff --git a/irc/server.go b/irc/server.go
index b9a79536..31b8b24e 100644
--- a/irc/server.go
+++ b/irc/server.go
@@ -710,17 +710,17 @@ func (server *Server) applyConfig(config *Config, initial bool) (err error) {
 
 	// updated caps get DEL'd and then NEW'd
 	// so, we can just add updated ones to both removed and added lists here and they'll be correctly handled
-	server.logger.Debug("server", "Updated Caps", strings.Join(updatedCaps.Strings(caps.Cap301, config.Server.capValues), " "))
+	server.logger.Debug("server", "Updated Caps", strings.Join(updatedCaps.Strings(caps.Cap301, config.Server.capValues, 0), " "))
 	addedCaps.Union(updatedCaps)
 	removedCaps.Union(updatedCaps)
 
 	if !addedCaps.Empty() || !removedCaps.Empty() {
 		capBurstSessions = server.clients.AllWithCapsNotify()
 
-		added[caps.Cap301] = addedCaps.Strings(caps.Cap301, config.Server.capValues)
-		added[caps.Cap302] = addedCaps.Strings(caps.Cap302, config.Server.capValues)
+		added[caps.Cap301] = addedCaps.Strings(caps.Cap301, config.Server.capValues, 0)
+		added[caps.Cap302] = addedCaps.Strings(caps.Cap302, config.Server.capValues, 0)
 		// removed never has values, so we leave it as Cap301
-		removed = removedCaps.Strings(caps.Cap301, config.Server.capValues)
+		removed = removedCaps.Strings(caps.Cap301, config.Server.capValues, 0)
 	}
 
 	for _, sSession := range capBurstSessions {