diff --git a/Objects/bytesobject.c b/Objects/bytesobject.c
index c95a46d..4c55294 100644
--- a/Objects/bytesobject.c
+++ b/Objects/bytesobject.c
@@ -1683,11 +1683,11 @@
         char* result_buf;
         PyObject* result;
 
-        if (PySlice_GetIndicesEx(item,
-                         PyBytes_GET_SIZE(self),
-                         &start, &stop, &step, &slicelength) < 0) {
+        if (PySlice_Unpack(item, &start, &stop, &step) < 0) {
             return NULL;
         }
+        slicelength = PySlice_AdjustIndices(PyBytes_GET_SIZE(self), &start,
+                                            &stop, step);
 
         if (slicelength <= 0) {
             return PyBytes_FromStringAndSize("", 0);