diff --git a/irc/chanserv.go b/irc/chanserv.go
index f63cfe21..361f394a 100644
--- a/irc/chanserv.go
+++ b/irc/chanserv.go
@@ -952,7 +952,7 @@ func csHowToBanHandler(service *ircService, server *Server, client *Client, comm
 	success = true
 	if len(collateralDamage) != 0 {
 		service.Notice(rb, fmt.Sprintf(client.t("Warning: this ban will affect %d other users:"), len(collateralDamage)))
-		for _, line := range utils.BuildTokenLines(400, collateralDamage, " ") {
+		for _, line := range utils.BuildTokenLines(maxLastArgLength, collateralDamage, " ") {
 			service.Notice(rb, line)
 		}
 	}
diff --git a/irc/handlers.go b/irc/handlers.go
index 6374ad3c..b15e011a 100644
--- a/irc/handlers.go
+++ b/irc/handlers.go
@@ -199,13 +199,17 @@ func authenticateHandler(server *Server, client *Client, msg ircmsg.Message, rb
 	// continue existing sasl session
 	rawData := msg.Params[0]
 
-	if len(rawData) > 400 {
+	// https://ircv3.net/specs/extensions/sasl-3.1:
+	// "The response is encoded in Base64 (RFC 4648), then split to 400-byte chunks,
+	// and each chunk is sent as a separate AUTHENTICATE command."
+	saslMaxArgLength := 400
+	if len(rawData) > saslMaxArgLength {
 		rb.Add(nil, server.name, ERR_SASLTOOLONG, details.nick, client.t("SASL message too long"))
 		session.sasl.Clear()
 		return false
-	} else if len(rawData) == 400 {
+	} else if len(rawData) == saslMaxArgLength {
 		// allow 4 'continuation' lines before rejecting for length
-		if len(session.sasl.value) >= 400*4 {
+		if len(session.sasl.value) >= saslMaxArgLength*4 {
 			rb.Add(nil, server.name, ERR_SASLFAIL, details.nick, client.t("SASL authentication failed: Passphrase too long"))
 			session.sasl.Clear()
 			return false
@@ -1062,7 +1066,7 @@ func extjwtHandler(server *Server, client *Client, msg ircmsg.Message, rb *Respo
 	tokenString, err := sConfig.Sign(claims)
 
 	if err == nil {
-		maxTokenLength := 400
+		maxTokenLength := maxLastArgLength
 
 		for maxTokenLength < len(tokenString) {
 			rb.Add(nil, server.name, "EXTJWT", msg.Params[0], serviceName, "*", tokenString[:maxTokenLength])
@@ -3149,7 +3153,7 @@ func userhostHandler(server *Server, client *Client, msg ircmsg.Message, rb *Res
 	returnedClients := make(ClientSet)
 
 	var tl utils.TokenLineBuilder
-	tl.Initialize(400, " ")
+	tl.Initialize(maxLastArgLength, " ")
 	for i, nickname := range msg.Params {
 		if i >= 10 {
 			break
diff --git a/irc/server.go b/irc/server.go
index 341623e1..955a9337 100644
--- a/irc/server.go
+++ b/irc/server.go
@@ -506,7 +506,9 @@ func (client *Client) getWhoisOf(target *Client, hasPrivs bool, rb *ResponseBuff
 
 	whoischannels := client.whoisChannelsNames(target, rb.session.capabilities.Has(caps.MultiPrefix), oper.HasRoleCapab("sajoin"))
 	if whoischannels != nil {
-		rb.Add(nil, client.server.name, RPL_WHOISCHANNELS, cnick, tnick, strings.Join(whoischannels, " "))
+		for _, line := range utils.BuildTokenLines(maxLastArgLength, whoischannels, " ") {
+			rb.Add(nil, client.server.name, RPL_WHOISCHANNELS, cnick, tnick, line)
+		}
 	}
 	if target.HasMode(modes.Operator) && operStatusVisible(client, target, oper != nil) {
 		tOper := target.Oper()