diff --git a/Include/sysmodule.h b/Include/sysmodule.h
index 29e7bffb0fe..1e4bff1cd86 100644
--- a/Include/sysmodule.h
+++ b/Include/sysmodule.h
@@ -34,6 +34,7 @@ PyObject *PySys_GetObject Py_PROTO((char *));
 int PySys_SetObject Py_PROTO((char *, PyObject *));
 FILE *PySys_GetFile Py_PROTO((char *, FILE *));
 void PySys_Init Py_PROTO((void));
+void PySys_SetArgv Py_PROTO((int, char **));
 
 extern DL_IMPORT(PyObject *) _PySys_TraceFunc, *_PySys_ProfileFunc;
 extern DL_IMPORT(int) _PySys_CheckInterval;