We generalise the RS braneworld model by taking into account a general stringy bulk containing
the scalar dilaton field and the two-form Kalb-Ramond field, apart from gravity. Assuming small
fluctuations around a RS background, the back-reacted warp factor is obtained. It is shown that
the fine tuning problem in connection with the Higgs mass reappears in a new guise and the
effective modular potential fails to stabilise the braneworld.