diff --git a/kike.c b/kike.c
index 7a2d6e5..2ad92a0 100644
--- a/kike.c
+++ b/kike.c
@@ -944,23 +944,66 @@ client_set_ping_timer (struct client *c)
 
 // --- IRC command handling ----------------------------------------------------
 
+static void
+irc_make_reply (struct client *c, int id, va_list ap, struct str *output)
+{
+	str_append_printf (output, ":%s %03d %s ",
+		c->ctx->server_name, id, c->nickname ? c->nickname : "");
+	str_append_vprintf (output,
+		irc_get_text (c->ctx, id, g_default_replies[id]), ap);
+}
+
 // XXX: this way we cannot typecheck the arguments, so we must be careful
 static void
 irc_send_reply (struct client *c, int id, ...)
 {
-	struct str tmp;
-	str_init (&tmp);
+	struct str reply;
+	str_init (&reply);
 
 	va_list ap;
 	va_start (ap, id);
-	str_append_printf (&tmp, ":%s %03d %s ",
-		c->ctx->server_name, id, c->nickname ? c->nickname : "");
-	str_append_vprintf (&tmp,
-		irc_get_text (c->ctx, id, g_default_replies[id]), ap);
+	irc_make_reply (c, id, ap, &reply);
 	va_end (ap);
 
-	client_send_str (c, &tmp);
-	str_free (&tmp);
+	client_send_str (c, &reply);
+	str_free (&reply);
+}
+
+/// Send a space-separated list of words across as many replies as needed
+static void
+irc_send_reply_vector (struct client *c, int id, char **items, ...)
+{
+	struct str common;
+	str_init (&common);
+
+	va_list ap;
+	va_start (ap, items);
+	irc_make_reply (c, id, ap, &common);
+	va_end (ap);
+
+	// We always send at least one message (there might be a client that
+	// expects us to send this message at least once)
+	do
+	{
+		struct str reply;
+		str_init (&reply);
+		str_append_str (&reply, &common);
+
+		// If not even a single item fits in the limit (which may happen,
+		// in theory) it just gets cropped.  We could also skip it.
+		if (*items)
+			str_append (&reply, *items++);
+
+		// Append as many items as fits in a single message
+		while (*items
+			&& reply.len + 1 + strlen (*items) <= IRC_MAX_MESSAGE_LENGTH)
+			str_append_printf (&reply, " %s", *items++);
+
+		client_send_str (c, &reply);
+		str_free (&reply);
+	}
+	while (*items);
+	str_free (&common);
 }
 
 #define RETURN_WITH_REPLY(c, ...)                                              \
@@ -1858,13 +1901,8 @@ irc_send_rpl_namreply (struct client *c, const struct channel *chan)
 		str_vector_add_owned (&nicks, str_steal (&result));
 	}
 
-	if (nicks.len)
-	{
-		// FIXME: split it into multiple messages if it's too long
-		char *reply = join_str_vector (&nicks, ' ');
-		irc_send_reply (c, IRC_RPL_NAMREPLY, type, chan->name, reply);
-		free (reply);
-	}
+	irc_send_reply_vector (c, IRC_RPL_NAMREPLY,
+		nicks.vector, type, chan->name, "");
 	str_vector_free (&nicks);
 }
 
@@ -2024,6 +2062,9 @@ irc_send_whois_reply (struct client *c, const struct client *target)
 	if (target->away_message)
 		irc_send_reply (c, IRC_RPL_AWAY, nick, target->away_message);
 
+	struct str_vector channels;
+	str_vector_init (&channels);
+
 	struct str_map_iter iter;
 	str_map_iter_init (&iter, &c->ctx->channels);
 	struct channel *chan;
@@ -2040,14 +2081,12 @@ irc_send_whois_reply (struct client *c, const struct client *target)
 			else if (channel_user->modes & IRC_CHAN_MODE_VOICE)
 				str_append_c (&item, '+');
 			str_append (&item, chan->name);
-			str_append_c (&item, ' ');
-
-			// TODO: try to merge the results into as few messages as possible
-			irc_send_reply (c, IRC_RPL_WHOISCHANNELS, nick, item.str);
-
-			str_free (&item);
+			str_vector_add_owned (&channels, str_steal (&item));
 		}
 
+	irc_send_reply_vector (c, IRC_RPL_WHOISCHANNELS, channels.vector, nick, "");
+	str_vector_free (&channels);
+
 	irc_send_reply (c, IRC_RPL_ENDOFWHOIS, nick);
 }