diff --git a/ASTPlayground/MainForm.pas b/ASTPlayground/MainForm.pas
index b839dc7..8db26ca 100644
--- a/ASTPlayground/MainForm.pas
+++ b/ASTPlayground/MainForm.pas
@@ -696,7 +696,7 @@ begin
 
     var TestEnv := FEnvironment.CreateEnvironment;
 
-    TestEnv.Define('fib', TAst.Block(FCurrUnboundAst));
+    TestEnv.Define('fib', FCurrUnboundAst);
 
     Memo1.Lines.Add('--- Naive recursive fib with AST---');