diff --git a/py/runtime.c b/py/runtime.c
index b506c6a54994d4d154ed91ba9688fe40d4e32cba..d97763adf0435fe95a377a8c40035b8730f7dc6f 100644
--- a/py/runtime.c
+++ b/py/runtime.c
@@ -453,7 +453,7 @@ py_obj_t rt_list_append(py_obj_t self_in, py_obj_t arg) {
         self->u_tuple_list.items = m_renew(py_obj_t, self->u_tuple_list.items, self->u_tuple_list.alloc);
     }
     self->u_tuple_list.items[self->u_tuple_list.len++] = arg;
-    return arg;
+    return py_const_none; // return None, as per CPython
 }
 
 py_obj_t rt_gen_instance_next(py_obj_t self_in) {