modio: Implement io.StringIO class.
diff --git a/py/modio.c b/py/modio.c
index d07dc6a..b8727e3 100644
--- a/py/modio.c
+++ b/py/modio.c
@@ -11,6 +11,8 @@
     // Note: mp_builtin_open_obj should be defined by port, it's not
     // part of the core.
     { MP_OBJ_NEW_QSTR(MP_QSTR_open), (mp_obj_t)&mp_builtin_open_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_BytesIO), (mp_obj_t)&mp_type_stringio },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_StringIO), (mp_obj_t)&mp_type_stringio },
 };
 
 STATIC const mp_obj_dict_t mp_module_io_globals = {