diff --git a/clientapi/routing/routing.go b/clientapi/routing/routing.go
index 5e691e8ec..8cd207b7a 100644
--- a/clientapi/routing/routing.go
+++ b/clientapi/routing/routing.go
@@ -509,14 +509,14 @@ func Setup(
 
 	// Defined outside of handler to persist between calls
 	// TODO: clear based on some criteria
-	roomHierarchyPaginationCache := new(RoomHierarchyPaginationCache)
+	roomHierarchyPaginationCache := NewRoomHierarchyPaginationCache()
 	v1mux.Handle("/rooms/{roomID}/hierarchy",
 		httputil.MakeAuthAPI("spaces", userAPI, func(req *http.Request, device *userapi.Device) util.JSONResponse {
 			vars, err := httputil.URLDecodeMapValues(mux.Vars(req))
 			if err != nil {
 				return util.ErrorResponse(err)
 			}
-			return QueryRoomHierarchy(req, device, vars["roomID"], rsAPI, roomHierarchyPaginationCache)
+			return QueryRoomHierarchy(req, device, vars["roomID"], rsAPI, &roomHierarchyPaginationCache)
 		}, httputil.WithAllowGuests()),
 	).Methods(http.MethodGet, http.MethodOptions)
 
diff --git a/roomserver/internal/query/query_room_hierarchy.go b/roomserver/internal/query/query_room_hierarchy.go
index d10cae25e..a59c834d6 100644
--- a/roomserver/internal/query/query_room_hierarchy.go
+++ b/roomserver/internal/query/query_room_hierarchy.go
@@ -43,10 +43,10 @@ func (querier *Queryer) QueryNextRoomHierarchyPage(ctx context.Context, walker r
 		return nil, nil, roomserver.ErrRoomUnknownOrNotAllowed{Err: fmt.Errorf("room is unknown/forbidden")}
 	}
 
-	var discoveredRooms []fclient.MSC2946Room
+	discoveredRooms := []fclient.MSC2946Room{}
 
-	// Copy unvisited and processed to avoid modifying walker
-	unvisited := []roomserver.RoomHierarchyWalkerQueuedRoom{}
+	// Copy unvisited and processed to avoid modifying original walker (which is typically in cache)
+	unvisited := make([]roomserver.RoomHierarchyWalkerQueuedRoom, len(walker.Unvisited))
 	copy(unvisited, walker.Unvisited)
 	processed := walker.Processed.Copy()