nouveau_event_put_locked(struct nouveau_event *event, int index,
                         struct nouveau_eventh *handler)
 {
-       if (!--event->index[index].refs)
-               event->disable(event, index);
+       if (!--event->index[index].refs) {
+               if (event->disable)
+                       event->disable(event, index);
+       }
        list_del(&handler->head);
 }
 
        spin_lock_irqsave(&event->lock, flags);
        if (index < event->index_nr) {
                list_add(&handler->head, &event->index[index].list);
-               if (!event->index[index].refs++)
-                       event->enable(event, index);
+               if (!event->index[index].refs++) {
+                       if (event->enable)
+                               event->enable(event, index);
+               }
        }
        spin_unlock_irqrestore(&event->lock, flags);
 }