diff --git a/DysonNetwork.Shared/Data/CloudFileReferenceObject.cs b/DysonNetwork.Shared/Data/CloudFileReferenceObject.cs
index 1937356..794b29d 100644
--- a/DysonNetwork.Shared/Data/CloudFileReferenceObject.cs
+++ b/DysonNetwork.Shared/Data/CloudFileReferenceObject.cs
@@ -45,7 +45,9 @@ public class CloudFileReferenceObject : ModelBase, ICloudFile
             Name = proto.Name,
             FileMeta = GrpcTypeHelper.ConvertByteStringToObject<Dictionary<string, object?>>(proto.FileMeta) ?? [],
             UserMeta = GrpcTypeHelper.ConvertByteStringToObject<Dictionary<string, object?>>(proto.UserMeta) ?? [],
-            SensitiveMarks = GrpcTypeHelper.ConvertByteStringToObject<List<ContentSensitiveMark>>(proto.SensitiveMarks) ?? [],
+            SensitiveMarks = proto.HasSensitiveMarks
+                ? GrpcTypeHelper.ConvertByteStringToObject<List<ContentSensitiveMark>>(proto.SensitiveMarks)
+                : [],
             MimeType = proto.MimeType,
             Hash = proto.Hash,
             Size = proto.Size,
@@ -75,7 +77,7 @@ public class CloudFileReferenceObject : ModelBase, ICloudFile
 
         // Convert user metadata
         proto.UserMeta = GrpcTypeHelper.ConvertObjectToByteString(UserMeta);
-        
+
         proto.SensitiveMarks = GrpcTypeHelper.ConvertObjectToByteString(SensitiveMarks);
 
         return proto;
diff --git a/DysonNetwork.Shared/Proto/file.proto b/DysonNetwork.Shared/Proto/file.proto
index 0ae27f9..34129b3 100644
--- a/DysonNetwork.Shared/Proto/file.proto
+++ b/DysonNetwork.Shared/Proto/file.proto
@@ -24,7 +24,7 @@ message CloudFile {
   bytes file_meta = 3;
   // User-defined metadata
   bytes user_meta = 4;
-  bytes sensitive_marks = 12;
+  optional bytes sensitive_marks = 12;
 
   // MIME type of the file
   string mime_type = 5;