diff --git a/bignum-next-prime.c b/bignum-next-prime.c
index 51481a71fad0bb8bf113713bd0e0a09abc5bf495..5b30d0f8343cac9cc6f6fa0675f8e0b6097a6601 100644
--- a/bignum-next-prime.c
+++ b/bignum-next-prime.c
@@ -47,6 +47,9 @@
 # define UNLIKELY(cond) cond
 #endif
 
+/* From some benchmarking using the examples nextprime(200!) and
+   nextprime(240!), it seems that it pays off to use a prime list up
+   to around 5000--10000 primes. */
 static const unsigned primes[] = {
 #if 0
   3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67,
@@ -62,7 +65,7 @@ static const unsigned primes[] = {
   797, 809, 811, 821, 823, 827, 829, 839, 853, 857, 859, 863, 877,
   881, 883, 887, 907, 911, 919, 929, 937, 941, 947, 953, 967, 971,
   977, 983, 991, 997
-#elif 0
+#elif 1
   3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59,
   61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137,
   139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227,
@@ -231,6 +234,7 @@ bignum_next_prime(mpz_t p, mpz_t n, unsigned count, unsigned prime_limit,
       if (progress)
 	progress(progress_ctx, '.');
 
+#if 1
       /* FIXME: I doubt this Fermat test saves any time. */
       /* Fermat test, with respect to 2 */
       mpz_set_ui(tmp, 2);
@@ -242,7 +246,7 @@ bignum_next_prime(mpz_t p, mpz_t n, unsigned count, unsigned prime_limit,
 	  
 	  continue;
 	}
-
+#endif
       if (progress)
 	progress(progress_ctx, '+');