diff --git a/sys/geom/geom_io.c b/sys/geom/geom_io.c
index 0ef547695810..20e31b9b921b 100644
--- a/sys/geom/geom_io.c
+++ b/sys/geom/geom_io.c
@@ -269,7 +269,7 @@ g_reset_bio(struct bio *bp)
 }
 
 void
-g_io_init()
+g_io_init(void)
 {
 
 	g_bioq_init(&g_bio_run_down);