diff --git a/DysonNetwork.Sphere/Poll/Poll.cs b/DysonNetwork.Sphere/Poll/Poll.cs
index a45ed70..9b0c1db 100644
--- a/DysonNetwork.Sphere/Poll/Poll.cs
+++ b/DysonNetwork.Sphere/Poll/Poll.cs
@@ -10,12 +10,12 @@ public class Poll : ModelBase
 {
     public Guid Id { get; set; } = Guid.NewGuid();
     public List<PollQuestion> Questions { get; set; } = new();
-    
+
     [MaxLength(1024)] public string? Title { get; set; }
     [MaxLength(4096)] public string? Description { get; set; }
-    
+
     public Instant? EndedAt { get; set; }
-    
+
     public Guid PublisherId { get; set; }
     [JsonIgnore] public Publisher.Publisher? Publisher { get; set; }
 }
@@ -32,15 +32,15 @@ public enum PollQuestionType
 public class PollQuestion : ModelBase
 {
     public Guid Id { get; set; } = Guid.NewGuid();
-    
+
     public PollQuestionType Type { get; set; }
     [Column(TypeName = "jsonb")] public List<PollOption>? Options { get; set; }
-    
+
     [MaxLength(1024)] public string Title { get; set; } = null!;
     [MaxLength(4096)] public string? Description { get; set; }
     public int Order { get; set; } = 0;
     public bool IsRequired { get; set; }
-    
+
     public Guid PollId { get; set; }
     [JsonIgnore] public Poll Poll { get; set; } = null!;
 }
@@ -48,7 +48,7 @@ public class PollQuestion : ModelBase
 public class PollOption
 {
     public Guid Id { get; set; } = Guid.NewGuid();
-    [Required] [MaxLength(1024)] public string Label { get; set; } = null!;
+    [Required][MaxLength(1024)] public string Label { get; set; } = null!;
     [MaxLength(4096)] public string? Description { get; set; }
     public int Order { get; set; } = 0;
 }
@@ -57,8 +57,8 @@ public class PollAnswer : ModelBase
 {
     public Guid Id { get; set; } = Guid.NewGuid();
     [Column(TypeName = "jsonb")] public Dictionary<string, JsonElement> Answer { get; set; } = null!;
-    
+
     public Guid AccountId { get; set; }
     public Guid PollId { get; set; }
-    [JsonIgnore] public Poll Poll { get; set; } = null!;
-}
\ No newline at end of file
+    [JsonIgnore] public Poll? Poll { get; set; }
+}
diff --git a/DysonNetwork.Sphere/Poll/PollService.cs b/DysonNetwork.Sphere/Poll/PollService.cs
index 11f4115..1e06615 100644
--- a/DysonNetwork.Sphere/Poll/PollService.cs
+++ b/DysonNetwork.Sphere/Poll/PollService.cs
@@ -51,7 +51,10 @@ public class PollService(AppDatabase db, ICacheService cache)
 
         var answer = await db.PollAnswers
             .Where(e => e.PollId == pollId && e.AccountId == accountId)
+            .AsNoTracking()
             .FirstOrDefaultAsync();
+        if (answer is not null)
+            answer.Poll = null;
 
         // Set the answer even it is null, which stands for unanswered
         await cache.SetAsync(cacheKey, answer, TimeSpan.FromMinutes(30));