diff --git a/peps/pep-0757.rst b/peps/pep-0757.rst
index f19c91b4005..95f9ad205b0 100644
--- a/peps/pep-0757.rst
+++ b/peps/pep-0757.rst
@@ -100,6 +100,9 @@ Export a Python integer as a digits array::
 
         // Read-only array of unsigned digits.
         const void *digits;
+
+        // Member used internally, must not be used for other purpose.
+        Py_uintptr_t _reserved;
     } PyLong_DigitArray;
 
     PyAPI_FUNC(int) PyLong_Export(PyObject *obj, PyLong_DigitArray *array);
@@ -107,6 +110,10 @@ Export a Python integer as a digits array::
 On CPython 3.14, no memory copy is needed, it's just a thin wrapper to
 expose Python int internal digits array.
 
+``PyLong_DigitArray._reserved`` stores a strong reference to the Python
+:class:`int` object to make sure that that structure remains valid until
+``PyLong_FreeExport()`` is called.
+
 
 PyLong_Export()
 ^^^^^^^^^^^^^^^