diff --git a/crypto/bio/bio_test.cc b/crypto/bio/bio_test.cc
index a3bfb2b..5cc75b5 100644
--- a/crypto/bio/bio_test.cc
+++ b/crypto/bio/bio_test.cc
@@ -263,7 +263,7 @@
   return true;
 }
 
-int main(void) {
+int main() {
   CRYPTO_library_init();
 
 #if defined(OPENSSL_WINDOWS)