diff --git a/block/elevator.c b/block/elevator.c
index a0afdd317cef..7be96bbe142c 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -766,7 +766,8 @@ 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);