diff --git a/OngekiFumenEditor/Base/Collections/SoflanList_CachedPositionList.cs b/OngekiFumenEditor/Base/Collections/SoflanList_CachedPositionList.cs
index c8be3104..fa2a64b3 100644
--- a/OngekiFumenEditor/Base/Collections/SoflanList_CachedPositionList.cs
+++ b/OngekiFumenEditor/Base/Collections/SoflanList_CachedPositionList.cs
@@ -69,8 +69,8 @@ private enum ChgEvt
 
         public IEnumerable<(TGrid TGrid, double speed, BPMChange curBpm)> GetCalculatableEvents(BpmList bpmList, bool isDesignModel)
         {
-            var sortList = new SortableCollection<(ITimelineObject timeline, ChgEvt evt), TGrid>(x => x.timeline.TGrid);
-            foreach (var timelineObject in this.FilterNull().AsEnumerable<ITimelineObject>().Concat(bpmList))
+            var sortList = new List<(ITimelineObject timeline, ChgEvt evt)>();
+            foreach (var timelineObject in CollectionHelper.MergeTwoSortedCollections<ITimelineObject, TGrid>(x => x.TGrid, this, bpmList))
             {
                 switch (timelineObject)
                 {