diff --git a/Doc/reference/datamodel.rst b/Doc/reference/datamodel.rst
index ddffbb3..41f6a77 100644
--- a/Doc/reference/datamodel.rst
+++ b/Doc/reference/datamodel.rst
@@ -66,6 +66,8 @@
    containing circular references.  See the documentation of the :mod:`gc`
    module for information on controlling the collection of cyclic garbage.
    Other implementations act differently and CPython may change.
+   Do not depend on immediate finalization of objects when they become
+   unreachable (ex: always close files).
 
 Note that the use of the implementation's tracing or debugging facilities may
 keep objects alive that would normally be collectable. Also note that catching