diff --git a/rsa-keygen.c b/rsa-keygen.c
index e4731d546eec469f4fcbef710ef4083347c3fe1a..c1bc2f206f120bf8e298f92e0208a280786e5140 100644
--- a/rsa-keygen.c
+++ b/rsa-keygen.c
@@ -62,6 +62,13 @@ static const unsigned long primes[NUMBER_OF_PRIMES] = {
   977, 983, 991, 997
 };
 
+/* FIXME: Tune and optimize this more cerefully.
+   
+   1. Avoid using % in the loop.
+
+   2. Tune the number of primes.
+*/
+
 /* NOTE: The mpz_nextprime in current GMP is unoptimized. */
 static void
 bignum_next_prime(mpz_t p, mpz_t n, int count,