diff --git a/modules/client/directory/room.cc b/modules/client/directory/room.cc
index 5c989affc..4a8192c29 100644
--- a/modules/client/directory/room.cc
+++ b/modules/client/directory/room.cc
@@ -73,6 +73,12 @@ resource::response
 put__directory_room(client &client,
                     const resource::request &request)
 {
+	if(request.parv.size() < 1)
+		throw m::NEED_MORE_PARAMS
+		{
+			"Room alias path parameter missing"
+		};
+
 	m::room::alias::buf room_alias
 	{
 		url::decode(room_alias, request.parv[0])
@@ -83,7 +89,23 @@ put__directory_room(client &client,
 		unquote(request.at("room_id"))
 	};
 
-	if(false)
+	if(!exists(room_id))
+		throw m::NOT_FOUND
+		{
+			"Room %s is not found here.",
+			string_view{room_id}
+		};
+
+	const m::room::power power{room_id};
+	if(!power(request.user_id, "", "m.room.aliases", room_alias.host()))
+		throw m::ACCESS_DENIED
+		{
+			"Insufficient power in %s to set alias %s",
+			string_view{room_id},
+			string_view{room_alias}
+		};
+
+	if(m::room::aliases::cache::has(room_alias))
 		throw m::error
 		{
 			http::CONFLICT, "M_EXISTS",
@@ -91,8 +113,43 @@ put__directory_room(client &client,
 			room_alias
 		};
 
+	const unique_buffer<mutable_buffer> buf
+	{
+		4_KiB //TODO: conf
+	};
+
+	json::stack out{buf};
+	json::stack::object content{out};
+	json::stack::array array
+	{
+		content, "aliases"
+	};
+
+	const m::room::aliases aliases{room_id};
+	aliases.for_each(room_alias.host(), [&array]
+	(const m::room::alias &alias)
+	{
+		array.append(alias);
+		return true;
+	});
+
+	array.append(room_alias);
+	array.~array();
+	content.~object();
+
+	const auto eid
+	{
+		m::send(room_id, request.user_id, "m.room.aliases", room_alias.host(), json::object
+		{
+			out.completed()
+		})
+	};
+
 	return resource::response
 	{
-		client, http::OK
+		client, json::members
+		{
+			{ "event_id", eid }
+		}
 	};
 }