--- a/plugins/muc/muc.lib.lua	Mon Jan 28 01:49:04 2019 +0100
+++ b/plugins/muc/muc.lib.lua	Mon Feb 04 09:28:02 2019 +0000
@@ -721,7 +721,7 @@
 	else -- Type is "get" or "set"
 		local current_nick = self:get_occupant_jid(from);
 		if not current_nick then
-			origin.send(st.error_reply(stanza, "cancel", "not-acceptable"));
+			origin.send(st.error_reply(stanza, "cancel", "not-acceptable", "You are not currently connected to this chat"));
 			return true;
 		end
 		if not occupant then -- recipient not in room
@@ -754,7 +754,7 @@
 	local type = stanza.attr.type;
 	if not current_nick then -- not in room
 		if type ~= "error" then
-			origin.send(st.error_reply(stanza, "cancel", "not-acceptable"));
+			origin.send(st.error_reply(stanza, "cancel", "not-acceptable", "You are not currently connected to this chat"));
 		end
 		return true;
 	end
@@ -1054,7 +1054,7 @@
 module:hook("muc-occupant-groupchat", function(event)
 	local role_rank = valid_roles[event.occupant and event.occupant.role or "none"];
 	if role_rank <= valid_roles.none then
-		event.origin.send(st.error_reply(event.stanza, "cancel", "not-acceptable"));
+		event.origin.send(st.error_reply(event.stanza, "cancel", "not-acceptable", "You are not currently connected to this chat"));
 		return true;
 	elseif role_rank <= valid_roles.visitor then
 		event.origin.send(st.error_reply(event.stanza, "auth", "forbidden"));