diff --git a/block/elevator.c b/block/elevator.c
index bc7baeec0d102014c07ec7308d54dbc2161e4ba9..9b72dc7c8a5c98dcde87dc0d7e42d9a56f447776 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -765,7 +765,8 @@ void elv_unregister(struct elevator_type *e)
 		read_lock(&tasklist_lock);
 		do_each_thread(g, p) {
 			task_lock(p);
-			e->ops.trim(p->io_context);
+			if (p->io_context)
+				e->ops.trim(p->io_context);
 			task_unlock(p);
 		} while_each_thread(g, p);
 		read_unlock(&tasklist_lock);