diff --git a/Modules/gdbmmodule.c b/Modules/gdbmmodule.c
index cfc6abc..a522059 100644
--- a/Modules/gdbmmodule.c
+++ b/Modules/gdbmmodule.c
@@ -36,7 +36,7 @@
 
 static PyTypeObject Dbmtype;
 
-#define is_dbmobject(v) ((v)->ob_type == &Dbmtype)
+#define is_dbmobject(v) (Py_Type(v) == &Dbmtype)
 #define check_dbmobject_open(v) if ((v)->di_dbm == NULL) \
     { PyErr_SetString(DbmError, "GDBM object has already been closed"); \
       return NULL; }
@@ -370,8 +370,7 @@
 }
 
 static PyTypeObject Dbmtype = {
-    PyObject_HEAD_INIT(0)
-    0,
+    PyVarObject_HEAD_INIT(0, 0)
     "gdbm.gdbm",
     sizeof(dbmobject),
     0,