diff --git a/Objects/object.c b/Objects/object.c
index ff6c497..81de3b8 100644
--- a/Objects/object.c
+++ b/Objects/object.c
@@ -160,7 +160,7 @@
         return (PyVarObject *) PyErr_NoMemory();
     }
 
-    Py_SIZE(op) = size;
+    Py_SET_SIZE(op, size);
     PyObject_Init((PyObject *)op, tp);
     return op;
 }