diff --git a/ex-6/main.c b/ex-6/main.c
index 6c6cd8e..ea2da25 100644
--- a/ex-6/main.c
+++ b/ex-6/main.c
@@ -149,6 +149,7 @@ int main(int argc, char **argv) {
       fprintf(stderr, "\t-b N\t\tThe number of θ bins.\n");
       fprintf(stderr, "\t-s SIGMA\tThe sigma of gaussian kernel.\n");
       fprintf(stderr, "\t-r N\t\tThe number of RL deconvolution rounds.\n");
+      fprintf(stderr, "\t-m MODE\t\tThe deconvolution mode: 'fft' or 'rl'.\n");
       fprintf(stderr, "\t-n MU\t\tThe mean (μ) of Poisson noise to add to the convolution.\n");
       return EXIT_FAILURE;
     }