diff --git a/src/pythoncapi_compat.h b/src/pythoncapi_compat.h
index c1044386..9fab3e56 100644
--- a/src/pythoncapi_compat.h
+++ b/src/pythoncapi_compat.h
@@ -1234,7 +1234,8 @@ typedef struct PyLong_DigitArray {
     PyObject *obj;
     int negative;
     size_t ndigits;
-    Py_digit *digits;
+    const Py_digit *digits;
+    const PyLongLayout *layout;
 } PyLong_DigitArray;
 
 typedef struct PyLongWriter PyLongWriter;