diff --git a/include/openssl/bn.h b/include/openssl/bn.h
index 295ca62..5ca8b85 100644
--- a/include/openssl/bn.h
+++ b/include/openssl/bn.h
@@ -687,9 +687,9 @@
 // BN_prime_checks_for_validation can be used as the |checks| argument to the
 // primarily testing functions when validating an externally-supplied candidate
 // prime. It gives a false positive rate of at most 2^{-128}. (The worst case
-// false positive rate for a single iteration is 1/4, so we perform 32
-// iterations.)
-#define BN_prime_checks_for_validation 32
+// false positive rate for a single iteration is 1/4 per
+// https://eprint.iacr.org/2018/749. (1/4)^64 = 2^{-128}.)
+#define BN_prime_checks_for_validation 64
 
 // BN_prime_checks_for_generation can be used as the |checks| argument to the
 // primality testing functions when generating random primes. It gives a false