diff --git a/sys/dev/ahci/ahciem.c b/sys/dev/ahci/ahciem.c
--- a/sys/dev/ahci/ahciem.c
+++ b/sys/dev/ahci/ahciem.c
@@ -479,7 +479,7 @@
 			else
 				ads->common.bytes[0] |= SES_OBJSTAT_NOTINSTALLED;
 			if (ch->disablephy)
-				ads->common.bytes[3] |= SESCTL_DEVOFF;
+				ads->bytes[2] |= SESCTL_DEVOFF;
 			ahci_putch(ch);
 		}
 		ccb->ccb_h.status = CAM_REQ_CMP;