Index: Modules/itertoolsmodule.c
===================================================================
--- Modules/itertoolsmodule.c	(revision 61284)
+++ Modules/itertoolsmodule.c	(working copy)
@@ -198,23 +198,33 @@
 {
 	_grouperobject *igo;
 
-	igo = PyObject_New(_grouperobject, &_grouper_type);
+	igo = PyObject_GC_New(_grouperobject, &_grouper_type);
 	if (igo == NULL)
 		return NULL;
 	igo->parent = (PyObject *)parent;
 	Py_INCREF(parent);
 	igo->tgtkey = tgtkey;
 	Py_INCREF(tgtkey);
-
+	PyObject_GC_Track(igo);
 	return (PyObject *)igo;
 }
 
+static int
+_grouper_traverse(_grouperobject *igo, visitproc visit, void *arg)
+{
+	Py_VISIT(igo->parent);
+	Py_VISIT(igo->tgtkey);
+	return 0;
+}
+
+
 static void
 _grouper_dealloc(_grouperobject *igo)
 {
+	PyObject_GC_UnTrack(igo);
 	Py_DECREF(igo->parent);
 	Py_DECREF(igo->tgtkey);
-	PyObject_Del(igo);
+	PyObject_GC_Del(igo);
 }
 
 static PyObject *
@@ -280,9 +290,9 @@
 	PyObject_GenericGetAttr,	/* tp_getattro */
 	0,				/* tp_setattro */
 	0,				/* tp_as_buffer */
-	Py_TPFLAGS_DEFAULT,		/* tp_flags */
+	Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC, /* tp_flags */
 	0,				/* tp_doc */
-	0, 				/* tp_traverse */
+	(traverseproc)_grouper_traverse,/* tp_traverse */
 	0,				/* tp_clear */
 	0,				/* tp_richcompare */
 	0,				/* tp_weaklistoffset */
@@ -299,7 +309,7 @@
 	0,				/* tp_init */
 	0,				/* tp_alloc */
 	0,				/* tp_new */
-	PyObject_Del,			/* tp_free */
+	PyObject_GC_Del,		/* tp_free */
 };
 
  
Index: Lib/test/test_itertools.py
===================================================================
--- Lib/test/test_itertools.py	(revision 61284)
+++ Lib/test/test_itertools.py	(working copy)
@@ -707,6 +707,13 @@
         a = []
         self.makecycle(takewhile(bool, [1, 0, a, a]), a)
 
+    def test_issue2246(self):
+        n = 10
+        keyfunc = lambda x: x
+        for i, j in groupby(xrange(n), key=keyfunc):
+            keyfunc.__dict__.setdefault('x',[]).append(j)
+        
+              
 def R(seqn):
     'Regular generator'
     for i in seqn: