diff --git a/hw/s390x/virtio-ccw.c b/hw/s390x/virtio-ccw.c
index 0e60270..8feb345 100644
--- a/hw/s390x/virtio-ccw.c
+++ b/hw/s390x/virtio-ccw.c
@@ -1237,6 +1237,7 @@
     .name = TYPE_VIRTIO_CCW_BUS,
     .parent = TYPE_VIRTIO_BUS,
     .instance_size = sizeof(VirtioCcwBusState),
+    .class_size = sizeof(VirtioCcwBusClass),
     .class_init = virtio_ccw_bus_class_init,
 };