diff --git a/server/gameserver/incubator.cc b/server/gameserver/incubator.cc
index ead84fff..50aa96fd 100644
--- a/server/gameserver/incubator.cc
+++ b/server/gameserver/incubator.cc
@@ -404,10 +404,12 @@ void Incubator::NextWave()
         int acc_time = 0;
         {
             xtimer_list* timer = wave_timers_[room->pve_data.GetWave()];
-            int remain_time = room->xtimer.GetRemainTime(timer);
-            room->xtimer.ModifyTimer
-                (timer, room->pve_mode_meta->pb->wave_prepare_time() * SERVER_FRAME_RATE);
-            acc_time = remain_time;
+            if (timer) {
+                int remain_time = room->xtimer.GetRemainTime(timer);
+                room->xtimer.ModifyTimer
+                    (timer, room->pve_mode_meta->pb->wave_prepare_time() * SERVER_FRAME_RATE);
+                acc_time = remain_time;
+            }
         }
         acc_time -= room->pve_mode_meta->pb->wave_prepare_time() * SERVER_FRAME_RATE;
         for (int i = room->pve_data.GetWave() + 1; i < wave_timers_.size(); ++i) {