diff --git a/src/comp/front/ast.rs b/src/comp/front/ast.rs
index 34df06add68..1425db61a24 100644
--- a/src/comp/front/ast.rs
+++ b/src/comp/front/ast.rs
@@ -117,6 +117,7 @@ tag ty_ {
     ty_char;
     ty_str;
     ty_box(@ty);
+    ty_tup(vec[tup(bool /* mutability */, @ty)]);
     ty_path(path, option[referent]);
 }