diff --git a/crypto/modes/gcm_test.c b/crypto/modes/gcm_test.c
index 8c52b85..a112431 100644
--- a/crypto/modes/gcm_test.c
+++ b/crypto/modes/gcm_test.c
@@ -413,7 +413,7 @@
   return ret;
 }
 
-int main() {
+int main(void) {
   int ret = 0;
   unsigned i;