diff --git a/nac3core/src/toplevel/builtins.rs b/nac3core/src/toplevel/builtins.rs
index 1c1228fc..30001443 100644
--- a/nac3core/src/toplevel/builtins.rs
+++ b/nac3core/src/toplevel/builtins.rs
@@ -1265,8 +1265,7 @@ pub fn get_builtins(primitives: &mut (PrimitiveStore, Unifier)) -> BuiltinInfo {
         })),
     ];
 
-    let ast_list: Vec<Option<ast::Stmt<()>>> =
-        (0..top_level_def_list.len()).map(|_| None).collect();
+    let ast_list: Vec<Option<ast::Stmt<()>>> = vec![None; top_level_def_list.len()];
     (
         izip!(top_level_def_list, ast_list).collect_vec(),
         &[