diff -r fd8dc3746992 Modules/_ctypes/callbacks.c
--- a/Modules/_ctypes/callbacks.c	Sat Jul 02 14:43:11 2011 +0200
+++ b/Modules/_ctypes/callbacks.c	Mon Jul 04 10:39:19 2011 +1000
@@ -13,6 +13,7 @@
 CThunkObject_dealloc(PyObject *_self)
 {
     CThunkObject *self = (CThunkObject *)_self;
+    PyObject_GC_UnTrack(self);
     Py_XDECREF(self->converters);
     Py_XDECREF(self->callable);
     Py_XDECREF(self->restype);