Spectrum-overlay scenarios for wideband multi-carrier (MC) systems bring new technical challenges that must be considered during the system design. In such a scenario, the receiver has to perform actions, such as channel estimation and synchronization, in the presence of possibly strong in-band interference. In this paper, we modify the iterative maximum likelihood joint frame synchronization and channel estimation algorithm for downlink MC-CDMA presented in [1] to have better performance in the presence of narrowband interference. The performance of the modified algorithm is verified through computer simulations and compared with the original one.