diff --git a/Objects/tupleobject.c b/Objects/tupleobject.c
index 2495e95..808156f 100644
--- a/Objects/tupleobject.c
+++ b/Objects/tupleobject.c
@@ -715,11 +715,11 @@
         PyObject* it;
         PyObject **src, **dest;
 
-        if (PySlice_GetIndicesEx((PySliceObject*)item,
-                         PyTuple_GET_SIZE(self),
-                         &start, &stop, &step, &slicelength) < 0) {
+        if (_PySlice_Unpack((PySliceObject *)item, &start, &stop, &step) < 0) {
             return NULL;
         }
+        slicelength = _PySlice_AdjustIndices(PyTuple_GET_SIZE(self), &start,
+                                            &stop, step);
 
         if (slicelength <= 0) {
             return PyTuple_New(0);