diff --git a/Include/sliceobject.h b/Include/sliceobject.h
index 8ab62dd..0405eda 100644
--- a/Include/sliceobject.h
+++ b/Include/sliceobject.h
@@ -38,6 +38,16 @@
 				    Py_ssize_t *start, Py_ssize_t *stop, 
 				    Py_ssize_t *step, Py_ssize_t *slicelength);
 
+#define PySlice_GetIndicesEx(slice, length, start, stop, step, slicelen) (  \
+    _PySlice_Unpack((PyObject *)(slice), (start), (stop), (step)) < 0 ? -1 :  \
+    ((*slicelen = _PySlice_AdjustIndices((length), (start), (stop), *(step))), \
+     0))
+PyAPI_FUNC(int) _PySlice_Unpack(PyObject *slice,
+                                Py_ssize_t *start, Py_ssize_t *stop, Py_ssize_t *step);
+PyAPI_FUNC(Py_ssize_t) _PySlice_AdjustIndices(Py_ssize_t length,
+                                              Py_ssize_t *start, Py_ssize_t *stop,
+                                              Py_ssize_t step);
+
 #ifdef __cplusplus
 }
 #endif