diff --git a/py/objattrtuple.c b/py/objattrtuple.c
index 04c17a2..c6dd3ae 100644
--- a/py/objattrtuple.c
+++ b/py/objattrtuple.c
@@ -50,17 +50,17 @@
 
 STATIC void mp_obj_attrtuple_print(const mp_print_t *print, mp_obj_t o_in, mp_print_kind_t kind) {
     (void)kind;
-    mp_obj_tuple_t *o = o_in;
-    const qstr *fields = (const qstr*)o->items[o->len];
+    mp_obj_tuple_t *o = MP_OBJ_TO_PTR(o_in);
+    const qstr *fields = (const qstr*)MP_OBJ_TO_PTR(o->items[o->len]);
     mp_obj_attrtuple_print_helper(print, fields, o);
 }
 
 STATIC void mp_obj_attrtuple_attr(mp_obj_t self_in, qstr attr, mp_obj_t *dest) {
     if (dest[0] == MP_OBJ_NULL) {
         // load attribute
-        mp_obj_tuple_t *self = self_in;
+        mp_obj_tuple_t *self = MP_OBJ_TO_PTR(self_in);
         mp_uint_t len = self->len;
-        const qstr *fields = (const qstr*)self->items[len];
+        const qstr *fields = (const qstr*)MP_OBJ_TO_PTR(self->items[len]);
         for (mp_uint_t i = 0; i < len; i++) {
             if (fields[i] == attr) {
                 dest[0] = self->items[i];
@@ -77,8 +77,8 @@
     for (mp_uint_t i = 0; i < n; i++) {
         o->items[i] = items[i];
     }
-    o->items[n] = (void*)fields;
-    return o;
+    o->items[n] = MP_OBJ_FROM_PTR(fields);
+    return MP_OBJ_FROM_PTR(o);
 }
 
 const mp_obj_type_t mp_type_attrtuple = {