diff --git a/tests/sys/aio/aio_test.c b/tests/sys/aio/aio_test.c
index c4a9fa1c8e15..f2c3610bdb88 100644
--- a/tests/sys/aio/aio_test.c
+++ b/tests/sys/aio/aio_test.c
@@ -222,7 +222,7 @@ setup_signal(void)
  * separate process
  */
 static struct sigevent*
-setup_thread()
+setup_thread(void)
 {
 	static struct sigevent sev;