diff --git a/sys/cam/cam_periph.c b/sys/cam/cam_periph.c
index 523e549a52e7..9ef359ca8186 100644
--- a/sys/cam/cam_periph.c
+++ b/sys/cam/cam_periph.c
@@ -734,6 +734,8 @@ cam_periph_mapmem(union ccb *ccb, struct cam_periph_map_info *mapinfo)
 	case XPT_CONT_TARGET_IO:
 		if ((ccb->ccb_h.flags & CAM_DIR_MASK) == CAM_DIR_NONE)
 			return(0);
+		KASSERT((ccb->ccb_h.flags & CAM_DATA_MASK) == CAM_DATA_VADDR,
+		    ("not VADDR for SCSI_IO %p %x\n", ccb, ccb->ccb_h.flags));
 
 		data_ptrs[0] = &ccb->csio.data_ptr;
 		lengths[0] = ccb->csio.dxfer_len;
@@ -743,6 +745,8 @@ cam_periph_mapmem(union ccb *ccb, struct cam_periph_map_info *mapinfo)
 	case XPT_ATA_IO:
 		if ((ccb->ccb_h.flags & CAM_DIR_MASK) == CAM_DIR_NONE)
 			return(0);
+		KASSERT((ccb->ccb_h.flags & CAM_DATA_MASK) == CAM_DATA_VADDR,
+		    ("not VADDR for ATA_IO %p %x\n", ccb, ccb->ccb_h.flags));
 
 		data_ptrs[0] = &ccb->ataio.data_ptr;
 		lengths[0] = ccb->ataio.dxfer_len;