diff --git a/LiteDB/Client/Mapper/BsonMapper.Serialize.cs b/LiteDB/Client/Mapper/BsonMapper.Serialize.cs
index ed26073b6..337890c8c 100644
--- a/LiteDB/Client/Mapper/BsonMapper.Serialize.cs
+++ b/LiteDB/Client/Mapper/BsonMapper.Serialize.cs
@@ -176,9 +176,13 @@ private BsonDocument SerializeDictionary(Type type, IDictionary dict, int depth)
             return o;
         }
 
+        //some settings
+        bool _useInterface=true;
+        
         private BsonDocument SerializeObject(Type type, object obj, int depth)
         {
-            var t = obj.GetType();
+            //var t = obj.GetType();
+            var t = _useInterface ? type : obj.GetType();
             var doc = new BsonDocument();
             var entity = this.GetEntityMapper(t);
 
@@ -209,4 +213,4 @@ private BsonDocument SerializeObject(Type type, object obj, int depth)
             return doc;
         }
     }
-}
\ No newline at end of file
+}