diff --git a/tools/virtio/virtio_test.c b/tools/virtio/virtio_test.c
index e626fa553c5a..6d25dcd2e97a 100644
--- a/tools/virtio/virtio_test.c
+++ b/tools/virtio/virtio_test.c
@@ -232,7 +232,7 @@ const struct option longopts[] = {
 	}
 };
 
-static void help()
+static void help(void)
 {
 	fprintf(stderr, "Usage: virtio_test [--help]"
 		" [--no-indirect]"