diff --git a/src/Serenity.Net.CodeGenerator/Models/Metadata/ApplicationMetadata.cs b/src/Serenity.Net.CodeGenerator/Models/Metadata/ApplicationMetadata.cs
index 60546c7f9f..cc6c22e5ce 100644
--- a/src/Serenity.Net.CodeGenerator/Models/Metadata/ApplicationMetadata.cs
+++ b/src/Serenity.Net.CodeGenerator/Models/Metadata/ApplicationMetadata.cs
@@ -74,7 +74,7 @@ private bool IsEqualIgnoreCase(string objectName1, string objectName2)
                 NormalizeTablename(objectName2), StringComparison.OrdinalIgnoreCase);
     }
 
-    private Dictionary<string, IRowMetadata> rowByTablename = new();
+    private readonly Dictionary<string, IRowMetadata> rowByTablename = new();
 
     public IRowMetadata GetRowByTablename(string tablename)
     {