diff --git a/clientapi/routing/room_hierarchy.go b/clientapi/routing/room_hierarchy.go
index 2884d2c32..cf9d43dd1 100644
--- a/clientapi/routing/room_hierarchy.go
+++ b/clientapi/routing/room_hierarchy.go
@@ -138,7 +138,7 @@ func QueryRoomHierarchy(req *http.Request, device *userapi.Device, roomIDStr str
 		walker = *cachedWalker
 	}
 
-	discoveredRooms, nextWalker, err := rsAPI.QueryNextRoomHierarchyPage(req.Context(), walker, limit)
+	discoveredRooms, _, nextWalker, err := rsAPI.QueryNextRoomHierarchyPage(req.Context(), walker, limit)
 
 	if err != nil {
 		switch err.(type) {
diff --git a/federationapi/routing/query.go b/federationapi/routing/query.go
index c2e63c1b9..dac9b1b34 100644
--- a/federationapi/routing/query.go
+++ b/federationapi/routing/query.go
@@ -146,7 +146,7 @@ func QueryRoomHierarchy(httpReq *http.Request, request *fclient.FederationReques
 	}
 
 	walker := roomserverAPI.NewRoomHierarchyWalker(types.NewServerNameNotDevice(request.Origin()), roomID, suggestedOnly, 1)
-	discoveredRooms, _, err := rsAPI.QueryNextRoomHierarchyPage(httpReq.Context(), walker, -1)
+	discoveredRooms, inaccessibleRooms, _, err := rsAPI.QueryNextRoomHierarchyPage(httpReq.Context(), walker, -1)
 
 	if err != nil {
 		switch err.(type) {
@@ -175,10 +175,9 @@ func QueryRoomHierarchy(httpReq *http.Request, request *fclient.FederationReques
 	return util.JSONResponse{
 		Code: 200,
 		JSON: fclient.RoomHierarchyResponse{
-			Room:     discoveredRooms[0],
-			Children: discoveredRooms[1:],
-			// TODO: Actually check which rooms the requesting server/user is not allowed to see.
-			InaccessibleChildren: []string{},
+			Room:                 discoveredRooms[0],
+			Children:             discoveredRooms[1:],
+			InaccessibleChildren: inaccessibleRooms,
 		},
 	}
 }
diff --git a/roomserver/api/api.go b/roomserver/api/api.go
index dffb6d479..b2b319244 100644
--- a/roomserver/api/api.go
+++ b/roomserver/api/api.go
@@ -141,7 +141,12 @@ type QueryRoomHierarchyAPI interface {
 	//
 	// If returned walker is nil, then there are no more rooms left to traverse. This method does not modify the provided walker, so it
 	// can be cached.
-	QueryNextRoomHierarchyPage(ctx context.Context, walker RoomHierarchyWalker, limit int) ([]fclient.RoomHierarchyRoom, *RoomHierarchyWalker, error)
+	QueryNextRoomHierarchyPage(ctx context.Context, walker RoomHierarchyWalker, limit int) (
+		hierarchyRooms []fclient.RoomHierarchyRoom,
+		inaccessibleRooms []string,
+		hierarchyWalker *RoomHierarchyWalker,
+		err error,
+	)
 }
 
 type QueryMembershipAPI interface {
diff --git a/roomserver/internal/query/query_room_hierarchy.go b/roomserver/internal/query/query_room_hierarchy.go
index 5f55980f0..6af86c3b5 100644
--- a/roomserver/internal/query/query_room_hierarchy.go
+++ b/roomserver/internal/query/query_room_hierarchy.go
@@ -39,9 +39,14 @@ import (
 //
 // If returned walker is nil, then there are no more rooms left to traverse. This method does not modify the provided walker, so it
 // can be cached.
-func (querier *Queryer) QueryNextRoomHierarchyPage(ctx context.Context, walker roomserver.RoomHierarchyWalker, limit int) ([]fclient.RoomHierarchyRoom, *roomserver.RoomHierarchyWalker, error) {
+func (querier *Queryer) QueryNextRoomHierarchyPage(ctx context.Context, walker roomserver.RoomHierarchyWalker, limit int) (
+	[]fclient.RoomHierarchyRoom,
+	[]string,
+	*roomserver.RoomHierarchyWalker,
+	error,
+) {
 	if authorised, _ := authorised(ctx, querier, walker.Caller, walker.RootRoomID, nil); !authorised {
-		return nil, nil, roomserver.ErrRoomUnknownOrNotAllowed{Err: fmt.Errorf("room is unknown/forbidden")}
+		return nil, []string{}, nil, roomserver.ErrRoomUnknownOrNotAllowed{Err: fmt.Errorf("room is unknown/forbidden")}
 	}
 
 	discoveredRooms := []fclient.RoomHierarchyRoom{}
@@ -173,7 +178,7 @@ func (querier *Queryer) QueryNextRoomHierarchyPage(ctx context.Context, walker r
 
 	if len(unvisited) == 0 {
 		// If no more rooms to walk, then don't return a walker for future pages
-		return discoveredRooms, nil, nil
+		return discoveredRooms, []string{}, nil, nil
 	} else {
 		// If there are more rooms to walk, then return a new walker to resume walking from (for querying more pages)
 		newWalker := roomserver.RoomHierarchyWalker{
@@ -185,7 +190,7 @@ func (querier *Queryer) QueryNextRoomHierarchyPage(ctx context.Context, walker r
 			Processed:     processed,
 		}
 
-		return discoveredRooms, &newWalker, nil
+		return discoveredRooms, []string{}, &newWalker, nil
 	}
 
 }