diff --git a/Include/methodobject.h b/Include/methodobject.h
index ea35d86..5dbe214 100644
--- a/Include/methodobject.h
+++ b/Include/methodobject.h
@@ -49,7 +49,7 @@
 
 PyAPI_FUNC(PyObject *) _PyCFunction_FastCallKeywords(PyObject *func,
     PyObject *const *stack,
-    Py_ssize_t nargs,
+    size_t nargsf,
     PyObject *kwnames);
 #endif
 
@@ -105,6 +105,7 @@
     PyObject    *m_self; /* Passed as 'self' arg to the C func, can be NULL */
     PyObject    *m_module; /* The __module__ attribute, can be anything */
     PyObject    *m_weakreflist; /* List of weak references */
+    vectorcallfunc vectorcall;
 } PyCFunctionObject;
 
 PyAPI_FUNC(PyObject *) _PyMethodDef_RawFastCallDict(