diff --git a/src/tutorial.test.ts b/src/tutorial.test.ts
index e763eb4..74b4f09 100644
--- a/src/tutorial.test.ts
+++ b/src/tutorial.test.ts
@@ -54,7 +54,7 @@ test('mutation', () => {
         initial: { nextId: 0, todos: [] as Todo[] },
     });
 
-    dux.mutation(addTodo, (state, description) => {
+    dux.addMutation(addTodo, (description) => (state) => {
         state.todos.unshift({ description, id: state.nextId, done: false });
         state.nextId++;
     });