diff --git a/Python/ceval.c b/Python/ceval.c
index 9cac771..bce86ab 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -5074,14 +5074,10 @@
    and silently boost values less than -PY_SSIZE_T_MAX-1 to -PY_SSIZE_T_MAX-1.
    Return 0 on error, 1 on success.
 */
-/* Note:  If v is NULL, return success without storing into *pi.  This
-   is because_PyEval_SliceIndex() is called by apply_slice(), which can be
-   called by the SLICE opcode with v and/or w equal to NULL.
-*/
 int
 _PyEval_SliceIndex(PyObject *v, Py_ssize_t *pi)
 {
-    if (v != NULL) {
+    if (v != Py_None) {
         Py_ssize_t x;
         if (PyIndex_Check(v)) {
             x = PyNumber_AsSsize_t(v, NULL);
@@ -5099,6 +5095,26 @@
     return 1;
 }
 
+int
+_PyEval_SliceIndexNotNone(PyObject *v, Py_ssize_t *pi)
+{
+    Py_ssize_t x;
+    if (PyIndex_Check(v)) {
+        x = PyNumber_AsSsize_t(v, NULL);
+        if (x == -1 && PyErr_Occurred())
+            return 0;
+    }
+    else {
+        PyErr_SetString(PyExc_TypeError,
+                        "slice indices must be integers or "
+                        "have an __index__ method");
+        return 0;
+    }
+    *pi = x;
+    return 1;
+}
+
+
 #define CANNOT_CATCH_MSG "catching classes that do not inherit from "\
                          "BaseException is not allowed"