simulation of FFT megacore in modelsim

I wish to first do a standalone simulation of the FFT megacore within modelsim. I first compile fft.v, fft.vo, fft_syn and the automatically generated testbench into the work folder. The simulations runs but it seems that the input_real.txt and input_imag.txt files aren't bein read into the simulation because sink_real and sink_imag remain empty. Do I need to include any additional libraries to get it to work?