diff --git a/Python/sysmodule.c b/Python/sysmodule.c
index 1255665..da4b6e1 100644
--- a/Python/sysmodule.c
+++ b/Python/sysmodule.c
@@ -159,7 +159,7 @@
     if (argFormat && argFormat[0]) {
         va_list args;
         va_start(args, argFormat);
-        eventArgs = Py_VaBuildValue(argFormat, args);
+        eventArgs = _Py_VaBuildValue_SizeT(argFormat, args);
         va_end(args);
         if (eventArgs && !PyTuple_Check(eventArgs)) {
             PyObject *argTuple = PyTuple_Pack(1, eventArgs);