diff -r bc1a178b3bc8 Doc/library/inspect.rst
--- a/Doc/library/inspect.rst	Sat Apr 18 05:54:02 2015 +0200
+++ b/Doc/library/inspect.rst	Thu Apr 23 08:36:11 2015 +0200
@@ -263,7 +263,10 @@
 
 .. function:: isgenerator(object)
 
-   Return true if the object is a generator.
+   Return true if the object is a generator.  Note that this returns
+   false for non-generator objects even if they implement the
+   :class:`collections.abc.Generator` protocol.  It is therefore
+   preferable to use ``isinstance(obj, Generator)`` instead.
 
 
 .. function:: istraceback(object)