diff --git a/sys/cam/ctl/ctl_frontend.c b/sys/cam/ctl/ctl_frontend.c
--- a/sys/cam/ctl/ctl_frontend.c
+++ b/sys/cam/ctl/ctl_frontend.c
@@ -162,7 +162,7 @@
 	if ((port_num < 0) ||
 	    (ctl_set_mask(softc->ctl_port_mask, port_num) < 0)) {
 		mtx_unlock(&softc->ctl_lock);
-		return (1);
+		return (EBUSY);
 	}
 	softc->num_ports++;
 	mtx_unlock(&softc->ctl_lock);