diff --git a/py/builtin.c b/py/builtin.c
index 56cb49d..333119b 100644
--- a/py/builtin.c
+++ b/py/builtin.c
@@ -364,3 +364,9 @@
 }
 
 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);
+}
+
+MP_DEFINE_CONST_FUN_OBJ_1(mp_builtin_id_obj, mp_builtin_id);
diff --git a/py/builtin.h b/py/builtin.h
index 4257de5..c6e453f 100644
--- a/py/builtin.h
+++ b/py/builtin.h
@@ -11,6 +11,7 @@
 MP_DECLARE_CONST_FUN_OBJ(mp_builtin_divmod_obj);
 MP_DECLARE_CONST_FUN_OBJ(mp_builtin_eval_obj);
 MP_DECLARE_CONST_FUN_OBJ(mp_builtin_hash_obj);
+MP_DECLARE_CONST_FUN_OBJ(mp_builtin_id_obj);
 MP_DECLARE_CONST_FUN_OBJ(mp_builtin_isinstance_obj);
 MP_DECLARE_CONST_FUN_OBJ(mp_builtin_issubclass_obj);
 MP_DECLARE_CONST_FUN_OBJ(mp_builtin_iter_obj);
diff --git a/py/qstrdefs.h b/py/qstrdefs.h
index 50b426f..8bf3936 100644
--- a/py/qstrdefs.h
+++ b/py/qstrdefs.h
@@ -57,6 +57,7 @@
 Q(filter)
 Q(float)
 Q(hash)
+Q(id)
 Q(int)
 Q(isinstance)
 Q(issubclass)
diff --git a/py/runtime.c b/py/runtime.c
index a3970fe..67bb90c 100644
--- a/py/runtime.c
+++ b/py/runtime.c
@@ -144,6 +144,7 @@
     mp_map_add_qstr(&map_builtins, MP_QSTR_divmod, (mp_obj_t)&mp_builtin_divmod_obj);
     mp_map_add_qstr(&map_builtins, MP_QSTR_eval, (mp_obj_t)&mp_builtin_eval_obj);
     mp_map_add_qstr(&map_builtins, MP_QSTR_hash, (mp_obj_t)&mp_builtin_hash_obj);
+    mp_map_add_qstr(&map_builtins, MP_QSTR_id, (mp_obj_t)&mp_builtin_id_obj);
     mp_map_add_qstr(&map_builtins, MP_QSTR_isinstance, (mp_obj_t)&mp_builtin_isinstance_obj);
     mp_map_add_qstr(&map_builtins, MP_QSTR_issubclass, (mp_obj_t)&mp_builtin_issubclass_obj);
     mp_map_add_qstr(&map_builtins, MP_QSTR_iter, (mp_obj_t)&mp_builtin_iter_obj);