diff --git a/Python/bltinmodule.c b/Python/bltinmodule.c
index 90fbb44..5de4363 100644
--- a/Python/bltinmodule.c
+++ b/Python/bltinmodule.c
@@ -29,7 +29,6 @@
 {
     Py_ssize_t i, j;
     PyObject *base, *meth, *new_base, *result, *new_bases = NULL;
-    PyObject *stack[1] = {bases};
     assert(PyTuple_Check(bases));
 
     for (i = 0; i < nargs; i++) {
@@ -55,7 +54,7 @@
             }
             continue;
         }
-        new_base = _PyObject_FastCall(meth, stack, 1);
+        new_base = _PyObject_CallOneArg(meth, bases);
         Py_DECREF(meth);
         if (!new_base) {
             goto error;
@@ -574,7 +573,7 @@
             ok = PyObject_IsTrue(item);
         } else {
             PyObject *good;
-            good = PyObject_CallFunctionObjArgs(lz->func, item, NULL);
+            good = _PyObject_CallOneArg(lz->func, item);
             if (good == NULL) {
                 Py_DECREF(item);
                 return NULL;
@@ -1625,7 +1624,7 @@
     while (( item = PyIter_Next(it) )) {
         /* get the value from the key function */
         if (keyfunc != NULL) {
-            val = PyObject_CallFunctionObjArgs(keyfunc, item, NULL);
+            val = _PyObject_CallOneArg(keyfunc, item);
             if (val == NULL)
                 goto Fail_it_item;
         }
@@ -2178,7 +2177,7 @@
     if (ndigits == NULL || ndigits == Py_None)
         result = _PyObject_CallNoArg(round);
     else
-        result = PyObject_CallFunctionObjArgs(round, ndigits, NULL);
+        result = _PyObject_CallOneArg(round, ndigits);
     Py_DECREF(round);
     return result;
 }