diff --git a/IRaCIS.Core.Application/Service/SiteSurvey/DTO/TrialSiteSurveyViewModel.cs b/IRaCIS.Core.Application/Service/SiteSurvey/DTO/TrialSiteSurveyViewModel.cs
index 24239eb23..5d23847f5 100644
--- a/IRaCIS.Core.Application/Service/SiteSurvey/DTO/TrialSiteSurveyViewModel.cs
+++ b/IRaCIS.Core.Application/Service/SiteSurvey/DTO/TrialSiteSurveyViewModel.cs
@@ -140,7 +140,7 @@ namespace IRaCIS.Core.Application.Contracts
         public bool IsDeleted { get; set; }
         public Guid Id { get; set; }
         public Guid TrialId { get; set; }
-        public Guid TrialSiteId { get; set; }
+        public Guid? TrialSiteId { get; set; }
         public DateTime CreateTime { get; set; }
         public Guid CreateUserId { get; set; }
         public DateTime UpdateTime { get; set; }