diff --git a/a8/xtimer.cc b/a8/xtimer.cc
index 416e06e..e3e20c6 100644
--- a/a8/xtimer.cc
+++ b/a8/xtimer.cc
@@ -236,6 +236,7 @@ namespace a8
                     timer->cb(TIMER_DELETE_EVENT, nullptr);
                 }
             }
+            timer->cb = nullptr;
             while (!list_empty(&timer->destory_handle_list)) {
                 XTimerDestoryHandleNode* node = list_first_entry(&timer->destory_handle_list,
                                                                  XTimerDestoryHandleNode,