diff --git a/IRaCIS.Core.Application/Service/Reading/ReadingImageTask/ReadingGlobalTaskService.cs b/IRaCIS.Core.Application/Service/Reading/ReadingImageTask/ReadingGlobalTaskService.cs
index 165e48f76..46fa86f47 100644
--- a/IRaCIS.Core.Application/Service/Reading/ReadingImageTask/ReadingGlobalTaskService.cs
+++ b/IRaCIS.Core.Application/Service/Reading/ReadingImageTask/ReadingGlobalTaskService.cs
@@ -96,13 +96,13 @@ namespace IRaCIS.Application.Services
 
                 await _readingGlobalTaskInfoRepository.BatchDeleteNoTrackingAsync(x => x.GlobalTaskId == inDto.GlobalTaskId && x.TaskId == visitTaskId && x.GlobalAnswerType == item.GlobalAnswerType && x.QuestionId == item.QuestionId);
 
-                await _readingTaskQuestionAnswerRepository.BatchUpdateNoTrackingAsync(x => x.VisitTaskId == item.VisitTaskId && x.ReadingQuestionTrialId == answer.QuestionId
-                && x.Answer != item.Answer && x.Answer != string.Empty
-                , x => new ReadingTaskQuestionAnswer()
-                {
-                    GlobalChangeAnswer = item.Answer,
-                    IsGlobalChange = true,
-                });
+                await _readingTaskQuestionAnswerRepository.BatchUpdateNoTrackingAsync(x => x.VisitTaskId == item.VisitTaskId && x.ReadingQuestionTrialId == item.QuestionId
+                   && x.Answer != item.Answer && item.Answer != string.Empty && item.Answer != null
+                   , x => new ReadingTaskQuestionAnswer()
+                   {
+                       GlobalChangeAnswer = item.Answer,
+                       IsGlobalChange = true,
+                   });
             }
 
             await _readingGlobalTaskInfoRepository.AddRangeAsync(inDto.QuestionList.Select(x => new ReadingGlobalTaskInfo()