--- a/plugins/mod_register.lua	Sat Sep 29 17:07:08 2012 +0100
+++ b/plugins/mod_register.lua	Mon Oct 01 21:07:20 2012 +0200
@@ -223,6 +223,12 @@
 					local host = module.host;
 					if not username or username == "" then
 						session.send(st.error_reply(stanza, "modify", "not-acceptable", "The requested username is invalid."));
+						return true;
+					end
+					local user = { username = username , host = host, allowed = true }
+					module:fire_event("user-registering", user);
+					if not user.allowed then
+						session.send(st.error_reply(stanza, "modify", "not-acceptable", "The requested username is forbidden."));
 					elseif usermanager_user_exists(username, host) then
 						session.send(st.error_reply(stanza, "cancel", "conflict", "The requested username already exists."));
 					else