I was writing something that iterates over all objects in gc.get_objects(). I don't know precisely where the offending tuple is coming from, but nearby objects in gc.get_objects() appear to be related to frozen_importlib. A tuple exists somewhere with a null pointer in it. Attempting to iterate over it or access its item results in a segmentation fault. I confirmed this on both Linux and OSX. Python 3.6.0a0 (default:778ccbe3cf74, Apr 20 2016, 20:17:38)