diff --git a/hugr-core/src/hugr/validate/test.rs b/hugr-core/src/hugr/validate/test.rs
index 3d68aac99..47c197416 100644
--- a/hugr-core/src/hugr/validate/test.rs
+++ b/hugr-core/src/hugr/validate/test.rs
@@ -1232,6 +1232,6 @@ mod extension_tests {
 
     fn make_tailloop(t: Type, es: ExtensionSet) -> DFGWrapper<Hugr, BuildHandle<TailLoopID>> {
         let row = TypeRow::from(t);
-        TailLoopBuilder::new(row.clone(), &[], row, es).unwrap()
+        TailLoopBuilder::new(row.clone(), type_row![], row, es).unwrap()
     }
 }