diff --git a/hw/s390x/css.h b/hw/s390x/css.h
index 7e53148..a09bb1f 100644
--- a/hw/s390x/css.h
+++ b/hw/s390x/css.h
@@ -81,6 +81,7 @@
     uint8_t ccw_no_data_cnt;
     /* transport-provided data: */
     int (*ccw_cb) (SubchDev *, CCW1);
+    void (*disable_cb)(SubchDev *);
     SenseId id;
     void *driver_data;
 };