diff --git a/Python/Python-ast.c b/Python/Python-ast.c
index d89b610..0ccf489 100644
--- a/Python/Python-ast.c
+++ b/Python/Python-ast.c
@@ -410,7 +410,7 @@
         }
         PyTuple_SET_ITEM(fnames, i, field);
     }
-    result = PyObject_CallFunction((PyObject*)&PyType_Type, "s(O){sOss}",
+    result = PyObject_CallFunction((PyObject*)&PyType_Type, "U(O){sOss}",
                     type, base, "_fields", fnames, "__module__", "_ast");
     Py_DECREF(fnames);
     return (PyTypeObject*)result;
diff --git a/Python/errors.c b/Python/errors.c
index e543506..b45dad4 100644
--- a/Python/errors.c
+++ b/Python/errors.c
@@ -608,7 +608,7 @@
 			goto failure;
 	}
 	/* Create a real new-style class. */
-	result = PyObject_CallFunction((PyObject *)&PyType_Type, "sOO",
+	result = PyObject_CallFunction((PyObject *)&PyType_Type, "UOO",
 				       dot+1, bases, dict);
   failure:
 	Py_XDECREF(bases);