diff --git a/compiler/rustc_ast/src/ast.rs b/compiler/rustc_ast/src/ast.rs
index ab8b7f632e8ef..cc0fc7b8358fb 100644
--- a/compiler/rustc_ast/src/ast.rs
+++ b/compiler/rustc_ast/src/ast.rs
@@ -2570,7 +2570,7 @@ pub enum AttrStyle {
 
 rustc_index::newtype_index! {
     #[custom_encodable]
-    #[debug_format = "AttrId({})]"]
+    #[debug_format = "AttrId({})"]
     pub struct AttrId {}
 }