Index: sys/cam/cam_xpt.c
===================================================================
--- sys/cam/cam_xpt.c
+++ sys/cam/cam_xpt.c
@@ -4264,8 +4264,10 @@
 		}
 		memcpy(ccb->casync.async_arg_ptr, async_arg, size);
 		ccb->casync.async_arg_size = size;
-	} else if (size < 0)
+	} else if (size < 0) {
+		ccb->casync.async_arg_ptr = async_arg;
 		ccb->casync.async_arg_size = size;
+	}
 	if (path->device != NULL && path->device->lun_id != CAM_LUN_WILDCARD)
 		xpt_freeze_devq(path, 1);
 	else