diff --git a/Include/datetime.h b/Include/datetime.h
index 059d5ecf7a2113..4da4ef0d8b2d5d 100644
--- a/Include/datetime.h
+++ b/Include/datetime.h
@@ -180,26 +180,9 @@ typedef struct {
 #define PyDateTime_CAPSULE_NAME "datetime.datetime_CAPI"
 
 
-#ifdef Py_BUILD_CORE
-
-/* Macros for type checking when building the Python core. */
-#define PyDate_Check(op) PyObject_TypeCheck(op, &PyDateTime_DateType)
-#define PyDate_CheckExact(op) (Py_TYPE(op) == &PyDateTime_DateType)
-
-#define PyDateTime_Check(op) PyObject_TypeCheck(op, &PyDateTime_DateTimeType)
-#define PyDateTime_CheckExact(op) (Py_TYPE(op) == &PyDateTime_DateTimeType)
-
-#define PyTime_Check(op) PyObject_TypeCheck(op, &PyDateTime_TimeType)
-#define PyTime_CheckExact(op) (Py_TYPE(op) == &PyDateTime_TimeType)
-
-#define PyDelta_Check(op) PyObject_TypeCheck(op, &PyDateTime_DeltaType)
-#define PyDelta_CheckExact(op) (Py_TYPE(op) == &PyDateTime_DeltaType)
-
-#define PyTZInfo_Check(op) PyObject_TypeCheck(op, &PyDateTime_TZInfoType)
-#define PyTZInfo_CheckExact(op) (Py_TYPE(op) == &PyDateTime_TZInfoType)
-
-#else
-
+/* When datetime.h is included from _datetimemodule.c,
+   the macros are defined in _datetimemodule.c. */
+#ifndef _PY_DATETIME_IMPL
 /* Define global variable for the C API and a macro for setting it. */
 static PyDateTime_CAPI *PyDateTimeAPI = NULL;
 
@@ -224,6 +207,8 @@ static PyDateTime_CAPI *PyDateTimeAPI = NULL;
 
 #define PyTZInfo_Check(op) PyObject_TypeCheck(op, PyDateTimeAPI->TZInfoType)
 #define PyTZInfo_CheckExact(op) (Py_TYPE(op) == PyDateTimeAPI->TZInfoType)
+#endif   /* !defined(_PY_DATETIME_IMPL) */
+
 
 /* Macros for accessing constructors in a simplified fashion. */
 #define PyDate_FromDate(year, month, day) \
@@ -264,8 +249,6 @@ static PyDateTime_CAPI *PyDateTimeAPI = NULL;
     PyDateTimeAPI->Date_FromTimestamp( \
         (PyObject*) (PyDateTimeAPI->DateType), args)
 
-#endif  /* Py_BUILD_CORE */
-
 #ifdef __cplusplus
 }
 #endif
diff --git a/Modules/_datetimemodule.c b/Modules/_datetimemodule.c
index bc4caa02d5f146..a986668332cc81 100644
--- a/Modules/_datetimemodule.c
+++ b/Modules/_datetimemodule.c
@@ -2,7 +2,12 @@
  *  http://www.zope.org/Members/fdrake/DateTimeWiki/FrontPage
  */
 
+/* When datetime.h is included from _datetimemodule.c,
+   the macros are defines in _datetimemodule.c. */
+#define _PY_DATETIME_IMPL
+
 #include "Python.h"
+#include "datetime.h"
 #include "structmember.h"
 
 #include <time.h>
@@ -11,14 +16,21 @@
 #  include <winsock2.h>         /* struct timeval */
 #endif
 
-/* Differentiate between building the core module and building extension
- * modules.
- */
-#ifndef Py_BUILD_CORE
-#define Py_BUILD_CORE
-#endif
-#include "datetime.h"
-#undef Py_BUILD_CORE
+#define PyDate_Check(op) PyObject_TypeCheck(op, &PyDateTime_DateType)
+#define PyDate_CheckExact(op) (Py_TYPE(op) == &PyDateTime_DateType)
+
+#define PyDateTime_Check(op) PyObject_TypeCheck(op, &PyDateTime_DateTimeType)
+#define PyDateTime_CheckExact(op) (Py_TYPE(op) == &PyDateTime_DateTimeType)
+
+#define PyTime_Check(op) PyObject_TypeCheck(op, &PyDateTime_TimeType)
+#define PyTime_CheckExact(op) (Py_TYPE(op) == &PyDateTime_TimeType)
+
+#define PyDelta_Check(op) PyObject_TypeCheck(op, &PyDateTime_DeltaType)
+#define PyDelta_CheckExact(op) (Py_TYPE(op) == &PyDateTime_DeltaType)
+
+#define PyTZInfo_Check(op) PyObject_TypeCheck(op, &PyDateTime_TZInfoType)
+#define PyTZInfo_CheckExact(op) (Py_TYPE(op) == &PyDateTime_TZInfoType)
+
 
 /*[clinic input]
 module datetime