diff --git a/Lagrange.Core/Message/Entities/LightAppEntity.cs b/Lagrange.Core/Message/Entities/LightAppEntity.cs
index 5315e78c3..c5043d284 100644
--- a/Lagrange.Core/Message/Entities/LightAppEntity.cs
+++ b/Lagrange.Core/Message/Entities/LightAppEntity.cs
@@ -23,9 +23,10 @@ public LightAppEntity(string payload)
     
     Elem[] IMessageEntity.Build()
     {
-        using var payload = new BinaryPacket();
+        var compressed = ZCompression.ZCompress(Encoding.UTF8.GetBytes(Payload));
+        using var payload = new BinaryPacket(1 + compressed.Length);
         payload.Write<byte>(0x01);
-        payload.Write(ZCompression.ZCompress(Encoding.UTF8.GetBytes(Payload)));
+        payload.Write(compressed);
 
         return new Elem[]
         {
diff --git a/Lagrange.Core/Message/MessageBuilder.cs b/Lagrange.Core/Message/MessageBuilder.cs
index f54ba6a7b..dbe539b46 100644
--- a/Lagrange.Core/Message/MessageBuilder.cs
+++ b/Lagrange.Core/Message/MessageBuilder.cs
@@ -93,7 +93,13 @@ public MessageBuilder Video(Stream video, Stream? thumbnail = null, bool dispose
         _entities.Add(new VideoEntity(video, thumbnail, disposeOnCompletion));
         return this;
     }
-    
+
+    public MessageBuilder LightApp(string json)
+    {
+        _entities.Add(new LightAppEntity(json));
+        return this;
+    }
+
     public static MessageBuilder operator +(MessageBuilder builder, IMessageEntity entity)
     {
         builder._entities.Add(entity);