diff --git a/src/ast/nodes.ts b/src/ast/nodes.ts
index ebedc68..59040bf 100644
--- a/src/ast/nodes.ts
+++ b/src/ast/nodes.ts
@@ -73,7 +73,7 @@ export type FieldDefinition =
 
 export abstract class Field extends ASTBase {}
 
-export const FieldBuiltinType = ['+', 'Type'] as const
+export const FieldBuiltinType = ['#', 'Type'] as const
 
 export class FieldBuiltinDef extends Field {
   constructor(