Change id to return signed integer.
diff --git a/py/builtin.c b/py/builtin.c
index 333119b..4564d15 100644
--- a/py/builtin.c
+++ b/py/builtin.c
@@ -366,7 +366,7 @@
 MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mp_builtin_bytes_obj, 1, 3, mp_builtin_bytes);
 
 static mp_obj_t mp_builtin_id(mp_obj_t o_in) {
-    return mp_obj_new_int_from_uint((machine_uint_t)o_in);
+    return mp_obj_new_int((machine_int_t)o_in);
 }
 
 MP_DEFINE_CONST_FUN_OBJ_1(mp_builtin_id_obj, mp_builtin_id);