diff --git a/src/boot/me/type.ml b/src/boot/me/type.ml
index 4969d86e88b..69010fdf7a2 100644
--- a/src/boot/me/type.ml
+++ b/src/boot/me/type.ml
@@ -107,7 +107,7 @@ let rec tyspec_to_str (ts:tyspec) : string =
           fmt_tyspec ff (!tv)
 
       | TYSPEC_exterior tv ->
-          fmt ff "@";
+          fmt ff "@@";
           fmt_tyspec ff (!tv)
 
       | TYSPEC_callable (out, ins) ->