#1410739: add a footnote about "is" and "unusual" behavior.
diff --git a/Doc/reference/expressions.rst b/Doc/reference/expressions.rst
index e393661..c815c0e 100644
--- a/Doc/reference/expressions.rst
+++ b/Doc/reference/expressions.rst
@@ -1113,7 +1113,7 @@
The operators :keyword:`is` and :keyword:`is not` test for object identity: ``x
is y`` is true if and only if *x* and *y* are the same object. ``x is not y``
-yields the inverse truth value.
+yields the inverse truth value. [#]_
.. _booleans:
@@ -1352,3 +1352,7 @@
only, but this caused surprises because people expected to be able to test a
dictionary for emptiness by comparing it to ``{}``.
+.. [#] Due to automatic garbage-collection, free lists, and the dynamic nature of
+ descriptors, you may notice seemingly unusual behaviour in certain uses of
+ the :keyword:`is` operator, like those involving comparisons between instance
+ methods, or constants. Check their documentation for more info.