Problem with arm_rfft_fast_f32

Hi I tested  arm_rfft_fast_f32 function from CMSIS-DSP 1.4.4 with generated 50hz sine wave at 1000Hz sample rate using 1024 samples, but i get peek value at 102, not 51 which i should get 1000/1024 ~0,97 * 51 = 50Hz:   uint16_t i;