diff --git a/src/tools/error_index_generator/main.rs b/src/tools/error_index_generator/main.rs
index 98eda97e236cb..373196b664281 100644
--- a/src/tools/error_index_generator/main.rs
+++ b/src/tools/error_index_generator/main.rs
@@ -22,7 +22,7 @@ macro_rules! register_diagnostics {
         pub fn error_codes() -> Vec<(&'static str, Option<&'static str>)> {
             let mut errors: Vec<(&str, Option<&str>)> = vec![
                 $((stringify!($error_code), Some($message)),)+
-                $((stringify!($undocumented), None),)+
+                $((stringify!($undocumented), None),)*
             ];
             errors.sort();
             errors