diff --git a/Include/objimpl.h b/Include/objimpl.h
index 03b6a8d..9f8523f 100644
--- a/Include/objimpl.h
+++ b/Include/objimpl.h
@@ -154,9 +154,9 @@
 /* Macros trading binary compatibility for speed. See also pymem.h.
    Note that these macros expect non-NULL object pointers.*/
 #define PyObject_INIT(op, typeobj) \
-	( (op)->ob_type = (typeobj), _Py_NewReference((PyObject *)(op)), (op) )
+	( Py_Type(op) = (typeobj), _Py_NewReference((PyObject *)(op)), (op) )
 #define PyObject_INIT_VAR(op, typeobj, size) \
-	( (op)->ob_size = (size), PyObject_INIT((op), (typeobj)) )
+	( Py_Size(op) = (size), PyObject_INIT((op), (typeobj)) )
 
 #define _PyObject_SIZE(typeobj) ( (typeobj)->tp_basicsize )
 
@@ -231,8 +231,8 @@
 #define PyType_IS_GC(t) PyType_HasFeature((t), Py_TPFLAGS_HAVE_GC)
 
 /* Test if an object has a GC head */
-#define PyObject_IS_GC(o) (PyType_IS_GC((o)->ob_type) && \
-	((o)->ob_type->tp_is_gc == NULL || (o)->ob_type->tp_is_gc(o)))
+#define PyObject_IS_GC(o) (PyType_IS_GC(Py_Type(o)) && \
+	(Py_Type(o)->tp_is_gc == NULL || Py_Type(o)->tp_is_gc(o)))
 
 PyAPI_FUNC(PyVarObject *) _PyObject_GC_Resize(PyVarObject *, Py_ssize_t);
 #define PyObject_GC_Resize(type, op, n) \
@@ -328,7 +328,7 @@
          && ((t)->tp_weaklistoffset > 0))
 
 #define PyObject_GET_WEAKREFS_LISTPTR(o) \
-	((PyObject **) (((char *) (o)) + (o)->ob_type->tp_weaklistoffset))
+	((PyObject **) (((char *) (o)) + Py_Type(o)->tp_weaklistoffset))
 
 #ifdef __cplusplus
 }