diff --git a/Doc/c-api/objbuffer.rst b/Doc/c-api/objbuffer.rst
index 13ccd6b..93f5ff0 100644
--- a/Doc/c-api/objbuffer.rst
+++ b/Doc/c-api/objbuffer.rst
@@ -23,6 +23,10 @@
 
    .. versionadded:: 1.6
 
+   .. versionchanged:: 2.5
+      This function used an :ctype:`int *` type for *buffer_len*. This might
+      require changes in your code for properly supporting 64-bit systems.
+
 
 .. cfunction:: int PyObject_AsReadBuffer(PyObject *obj, const void **buffer, Py_ssize_t *buffer_len)
 
@@ -34,6 +38,10 @@
 
    .. versionadded:: 1.6
 
+   .. versionchanged:: 2.5
+      This function used an :ctype:`int *` type for *buffer_len*. This might
+      require changes in your code for properly supporting 64-bit systems.
+
 
 .. cfunction:: int PyObject_CheckReadBuffer(PyObject *o)
 
@@ -52,3 +60,7 @@
 
    .. versionadded:: 1.6
 
+   .. versionchanged:: 2.5
+      This function used an :ctype:`int *` type for *buffer_len*. This might
+      require changes in your code for properly supporting 64-bit systems.
+